诺贝尔奖获得者全书【1904年】【生理学或医学奖】
【获奖类别】生理学或医学奖【获奖年代】1904年
【获得情况】伊万·彼德罗维奇·巴甫洛夫(Ivan Petrovich Pavlov)
[img]http://nobelprize.org/medicine/laureates/1904/pavlov.jpg[/img]
伊万·彼德罗维奇·巴甫洛夫(Ivan Petrovich Pavlov)
1849年9月14日出生于俄国梁赞
１９３６年２月２７日逝世
【获奖理由】 表彰他在消化生理学上的贡献对该学科的主要认识得到改变和扩展
【研究成果】他的科学贡献大致分三个时期，属于三个领域，即心脏生理、消化生理和高级神经活动生理。早年发现温血动物心脏有特殊的营养性神经，能使心跳增强或减弱。在消化腺的研究中，他设计了巴氏小胃等手术方法，有了这种方法，人们就可以对未麻醉的动物的消化液分泌等功能进行终身观察。在研究消化生理的过程中，形成了条件反射的概念，创立了条件反射学说。从而开辟了高级神经活动生理学的研究。从1903年起，连续三十余年，致力于这个新领域的发展。他发展了谢切诺夫关于心理活动反射本性的学说，把反射解释为有机体与外部世界相互作用的要素。他详细地研究了暂时神经联系形成的神经机制和条件反射活动发展与消退的规律性，论述了基本的神经生理过程——兴奋和抑制现象的扩散和集中及其相互诱导的规律，提出了神经系统类型的学说和两种信号系统的概念。他的条件反射理论是后来行为主义发展的奠基石，华生借此构成行为主义纲领。
【获奖感言】
生理学无冕之王——巴甫洛夫
１８９０年１０月的一天，在彼得堡军医学院里，一群大学生边走边议论着：
“今天是巴甫洛夫教授给我们上消化生理课，到时我们一定要请教一下，‘条件反射’！”一个学生兴奋地说道。“当然！巴甫洛夫是我们学院最年轻的教授，可以说是生理学方面的权威。”另一个学生应和道。
这群大学生来到教室后，见整个教室坐满了人。大家济济一堂，静等着巴甫洛夫教授的到来。
一阵铃声响过，从门口走进一位精壮的中年教授。大家不约而同地喊出：“巴甫洛夫教授！”
巴甫洛夫微笑着环视了一下教室，然后登上讲台，向大家鞠了一躬，接着便翻开教案，认真地上起课来。
这时，一个学生举手起立，朗声说道：“请问巴甫洛夫教授，什么是条件反射？”
话音刚落，同学们一下子把眼光都集中在这个发问的学生身上，弄得他十分不好意思，迟疑地坐了下来。紧接着，大家又把眼光转向巴甫洛夫教授，等待着他能回答这个问题。巴甫洛夫轻轻笑了一下，愉快地说道：“好吧！下边我给大家讲个故事……”他稍微停顿了一下，接着便讲了起来：从前，在俄国中部的梁赞城里，有户人家养了一条狗，主人怕这条狗乱跑，就用一根很粗的锁链把它锁了起来。从此，这条狗一见人就“汪汪”乱吠，并且呲牙咧嘴，表现非常凶恶。
一天，一群孩子走过这户人家，那条狗拚命的冲着他们狂吠，孩子们远远地躲了起来，谁也不敢接近它。
这时，一个脑袋很大的孩子向狗走去，他不但没躲，反而愈来愈靠近那条狗。
同伴们一齐惊讶地喊道：“不要靠近它！这畜生要咬人呢！”
“我去把锁链打开，它就不会再叫了！”这个孩子很坦然地说道。
“别打开！别打开！”小同伴们一面喊，一面吓得四散而逃。
孩子真的把锁链打开了。奇怪的是，它不仅不咬他，反而温顺地摇着尾巴，接受孩子的抚摸，从此，这条狗再也不凶恶地狂吠啦。
巴甫洛夫停了一下，看着一个个瞪大眼睛的学生问道：“大家知道这是因为什么吗？”
学生们摇摇头，仍然瞪着眼睛，静等教授的下文。
“其实，当时我也不知道原因，只是通过研究发现：套上锁链，对那条狗来说是一种刺激，也就是一种条件。这种条件引起了它保护自己的反射，因此这条狗变得异常凶恶。而一旦打开锁链，消除了这种条件，便不再引起它保护自己的反射，因此它变得温顺起来了。”同学们都露出了恍然大悟的神色，纷纷议论起来：
“原来那个孩子就是巴甫洛夫教授，真了不起！”
“噢！这就是条件反射，原来竟是这么简单！”
其实，他们哪里知道，巴甫洛夫为研究动物的消化生理付出了多少代价。
１８４９年，巴甫洛夫出生于梁赞城的一个贫苦的家庭，父亲是个传教士。１８７０年，２１岁的巴甫洛夫带着一张“贫困证明书”，进入了彼得堡大学攻读生理学。他刻苦学习，阅读大量的书籍，大学毕业时，获得了金质奖章。后来，又转到军医学院深造，并在这所学院中度过了４０多个年头。
在这期间，巴甫洛夫选择了研究消化系统的生理状况这个课题，开始长时间观察动物体内的消化活动。
他首先把狗的食道经过手术切断，把切断的食道两端缝在狗脖子的皮肤上，然后让狗饿上一段时间。
一天以后，巴甫洛夫把这只饥饿的狗拉到了实验室，在狗的面前放一盘鲜肉。狗一见鲜肉，便贪馋地吞了起来。然后咀嚼了几下就咽下去了。可是，不一会儿，咽下去的肉又掉到了食盘里。这是因为狗的食道已被切断，肉根本进不了胃里。
狗依然贪婪地吃着，盘子里的肉始终是那么多。
这只狗徒劳地吃了四五分钟后，奇怪的现象出现了，在通向狗胃的一根像皮管里流出了大量的胃液。
胃液不断分泌，是狗的第十对脑神经——迷走神经的冲动引起的。巴甫洛夫对这只狗的迷走神经也动过手术，已在上面引出一根丝线。现在，只要他稍微提动一下丝线，就切断了脑与胃之间的联系。结果，狗尽管还是在不断地吞咽鲜肉，但胃液却停止分泌了。
这就是著名的“假饲”实验，它可以使人们观察到狗的消化腺的分泌情况。
从２０世纪初，巴甫洛夫又开始研究高级神经活动，第一次发现了大脑皮层机能的活动规律。
他又给一条狗动了手术，在狗的腮帮子上开个小孔，用一根细细的导管安在它的一个唾液腺上。当狗吃东西流唾液的时候，一部分唾液就通过导管流到了外面。
巴甫洛夫通过实验发现，只要食物落到狗的口中，它就会泌出唾液，如果食物是湿的，分泌的唾液就少些，食物是干的，分泌的就多些。这种反射活动是狗和其它一切动物生来就有的，巴甫洛夫称它为非条件反射。
但后来的实验中，他又发现一个非常重要的事实，除了食物刺激口腔会引起狗的唾液分泌以外，其他的刺激，比如光、声音等的刺激，也能引起狗的唾液分泌。
为了通俗、形象地说明这种现象，在一次实验时，巴甫洛夫举起一只柠檬，对观看实验的学者说：
“诸位都知道这是柠檬，我不准备把它送到你们口中，只是让大家看一看……”
说到这里，所有在场的人的口中都流出了口水，许多人不自觉地咽了一下，并且笑出声来。
巴甫洛夫接着说：“诸位并没有吃到柠檬，却流出了口水。但诸位又是吃过柠檬的，知道它很酸，所以一见到它就流出了口水。这种流口水的反射是有条件的。因此我们称它为条件反射。”
从“非条件反射”到“条件反射”，巴甫洛夫经历了漫长而又艰苦的实验过程，这是消化生理过程中的一项重要发现，为人类在生理学方面的研究，做出了巨大的贡献。为此，在１９０４年，诺贝尔奖基金会该年度的生理学和医学奖金，授予了巴甫洛夫教授。要知道，巴甫洛夫是世界生理学家中第一个享有这种荣誉的科学家。
１９３５年，巴甫洛夫以８６岁的高龄，主持了在苏联召开的第１５届国际生理学大会，在这次大会上，巴甫洛夫被授予“全世界生物学界元老”的称号。次年２月，这位被人们赞颂为“生理学无冕之王”的科学家去世。
【其它事件】论人的艺术型和思维型
作者：巴甫洛夫
巴甫洛夫（1849——1936），苏联生理学家。彼得堡大学毕业，获军事医学院哲学博士学位。科学研究的贡献主要在心脏生理、消化生理和高级神经活动生理三个方面。晚年提出了两个信号系统学说。他的高级神经运动学说对于医学、心理学，以致于哲学都有影响。1904年获诺贝尔生理学和医学奖。著有《消化腺机能讲义》等。
我们在神经病院分析各种不同的神经官能症患者时，我得出了一个结论说，有两种人所特有的神经官能症，即歇斯底里和精神衰弱，并且我把这种结论与人的两种高级神经活动类型联系起来，即一种是艺术型，而且这是与动物相类似和接近的一种类型，因为动物也是仅以直接感受器来感知那表现为印象的全部外在世界的，而另一种类型乃是以第二信号系统工作的思维型。因此，人脑是由动物的大脑和表现为词的人的大脑部分所组成的。第二信号系统是从人类起开始占有优势的。可以设想，在某些不利的条件之下，在神经系统衰弱的情形之下，如果能重新进行大脑的种族分析的话，那未有的人就可能主要是运用第一信号系统，有的人可能主要是运用第二信号系统。这就把人的本性分为艺术的与纯理智的、抽象的两种。
如果这种分歧在各种不同的不利条件之下达到极大的程度时，那时人类高级神经活动的这种复杂性就发生病态表现，可以说，就成为夸张艺术家和夸张思想家（病理学）。我认为第一种相当于歇斯底里病人，第二种相当于精神衰弱患者。我曾经见过许多神经官能症患者。如果就这些病人的无生活能力和不活动情形说，则应当说，精神衰弱患者在生活上必定较歇斯底里病人更特别无能为力，这有种种事实证明。许多歇斯底里病人都会变成生活上的“大活动家”（就连那位创立某种特别宗教的美国女子说，她虽然是个典型的歇斯底里病人，但她也赚得了百万横财和声誉）①。相反地，那些只运用词的精神衰弱患者，就生活方面说，大部分是无论什么地方也都不适合，而是完全孤立无助的。当然也有生活达到极度混乱的歇斯底里病人，他们同样不能给自己找到生活位置，结果成为他自己和别人的一种负担。
①指曼丽·拜克-艾姬，“基督教科学”创始人。
我曾经给我自己提出这样一个问题，即我们的动物的情形是怎样呢？在动物中间，精神衰弱患者是不可能有的，因为它们没有第二信号系统。归根到底，人的一切复杂关系都已转变为第二信号系统了。我们已形成我们的词的、抽象的思维。第二信号系统是生活关系上最早的和最经常的调节器。动物没有这个调节器。它们的一切，直到最高峰的高级神经活动，都在于第一信号系统。人的第二信号系统，按照两条轨道去分别作用第一信号系统和皮质下部。第一，第二信号系统是以它的非常发展的、而为皮质下部所缺乏的、或者差不多缺乏的抑制（应想到在第一信号系统内，这种抑制是较不发展的）来发生作用；第二，第二信号系统是以它的积极活动——诱导规律——发生着作用。既然我们的活动都被集中到词的部分内——第二信号系统内——所以第二信号系统的诱导作用就必定要作用于第一信号系统和皮质下部。
动物不可能有这样类似的关系。不过这样的关系可以表现为这种形式，即抑制过程在第一信号系统内（动物的第一信号系统是在皮质下部上面）或许是很微弱的。如果就动物说，第一信号系统也是这种皮质下部的调节器的话，就能够形成实际上类似于歇斯底里病人情况的关系，而且如果在动物的第一信号系统内抑制过程是很微弱的话，就会使皮质下部发生一种不适合于外来刺激物作用条件的骚扰。可见，动物也许有某种类似于歇斯底里病人的东西。这就是说，我们人有第二信号系统对于第一信号系统和皮质下部的压力，而动物只有第一信号系统对于皮质下部的压力。实质虽然是相同的，不过在后一种场合，其抑制来源是惟一的，而在前一种场合，其抑制来源则是双重的（一部分渊源于积极系统，另一部分渊源于主动的活动）。
在柯尔土什庄有一只叫“威尔尼”的狗使我发生了这种想法。这是一条真正狂躁的不可抑制型的狗。“威尔尼”是一种警犬型的狗。它除了主人以外，不许任何人接近。它的食物反射是狂暴的。我们从它身上久已得不到多少还勉强过得去的条件反射系统了。这很类似玛·卡①的那只阉割了的狗的情形。不管刺激物的强度怎样，也不管分化完全与否，总常常出现超反常相。在错后时期，即在条件刺激物发生孤立作用的时期内，其反射过程是令人感觉兴趣的：在头五秒钟，它分泌出大量的条件唾液来，而在后五秒钟则完全没有这种条件唾液（即等于零）。我愿意说，这是歇斯底里病者，它那调节着神经系统和皮质下部能量的第一信号系统是完全无能为力的。在这里，在信号系统作用与皮质下部的情绪基调之间缺乏适应性。这是可以证明的，如果我们加强了第一信号系统内的抑制时（用溴素），那时它的秩序就会建立起来了。如果用6克的大量药剂时，我们就可以大大地调整这种混乱状态。
①即玛丽亚·卡比托诺夫娜·彼特洛娃，苏联学者。
因此，在实际上，很可能把“威尔尼”认为是歇斯底里病患者而忽视它，认为它对于这种皮质下部情绪基调并没有多少显著重要的调节器。
研究文献原文存放：
《心脏的传出神经》 (1883)、
《主要消化腺机能讲义》 (1897)、
《消化腺作用》 (1902)、
《动物高级神经活动(行为)客观研究20年经验：条件反射》 (1923)、
《大脑两半球机能讲义》 (1927)等。
巴甫洛夫 的讲演稿（Prize Lecture）:
Ivan Pavlov – Nobel Lecture
Nobel Lecture, December 12, 1904
Physiology of Digestion
It is not accidental that all phenomena of human life are dominated by the search for daily bread - the oldest link connecting all living things, man included, with the surrounding nature. Food finding its way into the organism where it undergoes certain changes - is decomposed, enters into new combinations and again dissociates - represents the process of life in all its fullness, from such elementary physical properties of the organism as weight, inertia, etc., all the way to the highest manifestations of human nature. Precise knowledge of what happens to the food entering the organism must be the subject of ideal physiology, the physiology of the future. Present-day physiology can but engage in the continuous accumulation of material for the achievement of this distant aim.
The first stage through which the food substances introduced from without must pass, is the digestive canal; the first vital action on these substances, or to be more exact and objective, their first participation in life, in its process, constitutes what we call the digestion.
The digestive canal represents a tube passing through the entire organism and communicating with the external world, i.e. as it were the external surface of the body, but turned inwards and thus hidden in the organism.
The physiologist who succeeds in penetrating deeper and deeper into the digestive canal becomes convinced that it consists of a number of chemical laboratories equipped with various mechanical devices.
The mechanical apparatuses are formed by muscular tissue that is a constituent part of the wall of the digestive canal. They either take care of the passage of the components of food from one laboratory to another, or detain them for a certain time in a given laboratory or, finally, expel them when they prove harmful to the organism; moreover, they participate in the mechanical processing of the food, aiding the chemical action on it by thorough mixing, etc.
A special, so-called glandular tissue which is either also a constituent part of the wall of the digestive canal, or lies beyond it in the shape of separate masses and communicates with it by means of tubes, produces chemical reagents, the so-called digestive juices that flow into separate segments of the digestive tract. The reagents are, on the one hand, aqueous solutions of such well-known chemical substances as hydrochloric acid, soda, etc., on the other hand, however, substances which are found only in a living organism and which break up the main components of food (proteins, carbohydrates, and fats) with such ease (so rapidly, at such a low temperature, and in such small quantities) as no other chemically well-studied substance could perform. These substances which act in vitro just as well as in the digestive canal, and which, therefore, are objects of chemical investigation entirely subject to laws, have so far, however, defied chemical analysis. As is known, they are called ferments.
From this general description of the digestive process I shall turn to facts relating to this process established by me and by the laboratory of which I am in charge. In doing so I deem it my duty to recall with profound gratitude my numerous laboratory co-workers.
It is perfectly clear that successful study of the digestive process, as of any other function of the organism, depends to a considerable degree on whether we succeed in finding the nearest and most convenient point of view on the process under observation and in removing all intervening processes between the phenomena under observation and the observer.
In order to investigate the production of secretion in the big digestive glands, that communicate with the digestive canal only by means of tubes, we cut from the wall of the digestive canal small pieces, in the centre of which were the normal openings of the secretory ducts; we then closed the opening in the wall of the canal by stitching, and the excised pieces were sutured to the corresponding site on the surface of the skin with the openings of the secretory ducts to the outside. Thanks to this procedure the juice was diverted from the digestive canal and could be collected in special vessels. In order to collect the juice produced by those microscopic glands that are located directly in the wall of the digestive canal, already since a long time large pieces were cut out from the wall of the digestive canal and artificial pouches with openings to the outside were made; the defect in the digestive canal, of course, was closed by stitching. In the case of the stomach, however, the nerves of the glandular cells were always severed when constructing an artificially isolated pouch and this, naturally, affected the normal work of the stomach. Taking into account the more delicate anatomical relations, we modified the operation in such a way that the normal nervous paths were left fully intact when making the isolated stomach-wall pouch.
Finally, as the digestive canal is a complex system, a series of separate chemical laboratories, I cut the connections between them in order to investigate the course of phenomena in each particular laboratory; thus I resolved the digestive canal into several separate parts. This, of course, necessitated laying short and convenient passage-ways from the outside into each separate laboratory. For this purpose metal tubes have long been in use; these coalesce with the skin in artificial body openings, and during the intervals between the experiments they can be sealed by means of plugs.
In this way we often had to perform very minute operations, sometimes several of them on one and the same animal. It goes without saying that the desire to accomplish the task with more confidence, to avoid wasting time and labour, and to spare our experimental animals as much as possible, made us strictly observe all the precautions taken by surgeons in respect to their patients. Here, too, we had to apply appropriate anaesthesia, observe scrupulous cleanliness during the operation, provide clean dwellings after the operation, and take thorough care of the wounds. But these measures did not suffice. After remaking the animal's organism in accordance with our design, which naturally caused more or less damage to the experimental animal, we had to find a modus vivendi for it that would ensure an absolutely normal and long life. Only by observing this condition would the results of our work be regarded as fully conclusive and as having elucidated the normal course of the phenomena. We succeeded thanks to our correct appraisal of the changes evoked in the organism, and thanks to the expedient measures taken by us; our healthy and happy animals did their laboratory work with real gusto; they always eagerly moved from their cages to the laboratory and readily jumped onto the tables where our experiments and observations were conducted. Believe me, I am not exaggerating. Thanks to our present surgical methods in physiology we can demonstrate at any time almost all phenomena of digestion without the loss of even a single drop of blood, without a single scream from the animal undergoing the experiment. At the same time this is an extremely important practical application of the power of human knowledge, which may also be of immediate use to man, who, due to the implacable fortuities of life, is often mutilated in similar, though more varied ways.
In our observations on dogs, we soon noticed the following fundamental fact: the kind of substances getting into the digestive canal from the external world, i.e. whether edible or inedible, dry or liquid, as well as the composition of the food determined on the onset or else absence of the work of the digestive glands, the peculiarities of their functioning in the former case, the amount of reagents produced by them, and their condition. This can be shown by a number of examples. Take, for instance, the production of saliva by the mucous salivary glands. With each meal, when edible substances find their way into the oral cavity, thick and viscous saliva containing much mucus flows out of these glands. With the introduction into the animal's mouth of substances that it finds repugnant, such as salt, acid, mustard, etc., the saliva may flow in the same quantity as in the first case, but now its quality is quite different - it is fluid and watery. If the dog is given now meat, then ordinary bread, other conditions being equal, the secretion of saliva in the second case will be more abundant than in the first. Similarly, of the substances for which the animal has a distaste some, for example chemical irritants like acid, alkali, etc., evoke a more profuse secretion of saliva than other, chemically indifferent substances, like bitters; consequently here, too, different activity of the salivary glands is observed. The gastric glands react in the same way; they secrete their juice now in larger, now in smaller quantities, now of a higher and now of a lower acidity and content of protein-dissolving ferment, so-called pepsin. Bread evokes the secretion of gastric juice with the highest ferment content, but of lowest acidity; milk evokes the minimum ferment content, while meat evokes the maximum acid content. For a certain quantity of protein if provided in the form of bread, the glands produce from two to four times as much as when provided in the form of meat or milk.
However, the diversity of the work of the gastric glands is not confined to the above-mentioned phenomena; it is manifested also in peculiar fluctuations in the quantity and quality of the reagent during the period of the functioning of the glands following the introduction of one or another food substance.
But that will suffice. I should only abuse your attention by giving an exposition of all the facts collected by us in this field. I shall merely mention that we observed similar correlations in relation to the other glands of the digestive tract.
Now it may further be asked: what does this changeability in the work of the glands signify? In reply we shall revert to the phenomenon of salivary secretion. Edible substances evoke the secretion of thick, concentrated saliva. Why? The answer, obviously, is that this enables the mass of food to pass smoothly through the tube leading from the mouth into the stomach. Under the action of certain substances disagreeable to the dog the same glands secrete fluid saliva. What purpose does the saliva serve in such cases? Apparently, either to dilute these substances and thereby weaken their chemically irritating action, or, as we know from our own experience, to cleanse the mouth from such substances. In this case exclusively water, not mucus, is required, and water is actually secreted.
As we have seen, bread, and especially dry bread, evokes secretion of considerably larger quantities of saliva than meat. This, too, is perfectly understandable: the eating of dry bread requires saliva, firstly, to dissolve the components of the bread and so make it possible to recognize its taste (something utterly inedible might have gotten into the mouth), and secondly, to soften the hard and dry bread, otherwise it would go down with difficulty and could even cause injury to the walls of the oesophagus while moving from the mouth into the stomach.
The relations inside the stomach are exactly the same. The bread protein induces secretion of more protein ferment than the protein of milk or meat, and a corresponding phenomenon is observed in the test tube: protein of meat and milk is broken up more easily by the protein ferment than vegetable protein.
Here again I could cite numerous additional examples of similar purposeful relationships between the work of the digestive glands and the properties of the substances entering the digestive tract (but this I shall do on a future occasion). There is nothing surprising at all in this phenomenon; and other relations would not be expected. It is clear to all that the animal organism is a highly complex system consisting of an almost infinite series of parts connected both with one another and, as a total complex, with the surrounding world, with which it is in a state of equilibrium. The equilibrium of this system, as of any other system, is a condition for its existence. And if in certain cases we are unable to disclose the purposeful relations in this system, the reason is that we lack knowledge; it does not mean at all that these relations are absent in the system during its continual existence.
Now we shall pass to a further question which arises from what has been said above: how is this equilibrium effected? Why is it that the glands produce and secrete in the digestive tract the very reagents needed for the successful treatment of the respective object? Apparently, it should be assumed that in some way certain properties of the object act on the gland, evoke in it a specific reaction and cause its specific activity. Analysis of this influence on the gland is an extremely intricate matter and one that requires much time. The main thing is to reveal in the object those properties which, in this particular case, act as stimuli on the glands in question. An investigation of this kind is not at all so easy as it looks at first sight. Here are some facts to prove this. By means of the previously mentioned metal tube, we introduce meat into the empty and inactive stomach of the dog, without the animal noticing it. In a few minutes the gastric reagent, an acid solution of the gastric protein ferment, begins to exude from the walls of the stomach. Which property of the meat lump has acted as the stimulus on the gastric glands? The simplest way would be to assume that this action has been caused by its mechanical properties-pressure, or friction against the walls of the stomach. But such an assumption would be absolutely wrong. Mechanical influences are completely ineffective with regard to the gastric glands. We can mechanically influence the wall of the stomach in any way - strongly or feebly, continuously or with interruptions, on limited areas or in a diffused way - but without obtaining a single drop of gastric juice. Actually, it is the components of meat soluble in water that are the stimulating substances. However, as yet we lack exact knowledge of these substances since the extractable substances of meat form a large group that still awaits investigation in full measure.
Here is one more example. A few minutes after the thyme finds its way into the next section of the digestive canal - into the duodenum - one of the glands of this section comes into action; this is the pancreas, a large organ located at the side of the digestive tract and connected with it by an excretory duct. But which of the properties of the thyme advancing in the intestine acts as a stimulating agent on this gland? Contrary to our expectations, it turned out that this action was exerted not by the properties of the juice which joined it in the stomach, namely, by its acid content. If we pour into the stomach or directly into the intestine pure gastric juice, or simply the acid which it contains, or even some other acid, our gland will begin to function just as vigorously, or even more vigorously, than in the case of the normal thyme passing from the stomach into the intestine. The profound significance of this unexpected fact is quite clear.
The gastric laboratory uses its protein ferment under an acid reaction. Different intestinal ferments, and among them, naturally, pancreatic ferments, cannot develop their activity in an acid medium. Hence, it is clear that the first task of the laboratory is to provide the neutral or alkaline reaction necessary for its successful activity. These circumstances are effected by the above-mentioned interrelations, since the acid content of the stomach, as already stated, induces secretion of alkaline pancreatic juice (and the higher the acid content, the greater the secretion). Thus, the pancreatic juice acts above all as a solution of soda.
One more example. It has been known for a long time that the pancreatic juice contains all the three ferments which act on the major food substances - a protein ferment, which is different from the gastric ferment, a starch ferment and a fat ferment. As proved by our experiments, the protein ferment in the pancreatic juice is, constantly or at times, entirely or partly (this is still a matter of argument), in an inactive, latent form. This may be justified by the fact that the active protein ferment might endanger the other two pancreatic ferments and destroy them. Simultaneously we established that the walls of the upper section of the intestine secrete a special fermentative substance the action of which is to transform the inactive pancreatic protein ferment into an active one. The active ferment, upon coming into contact with the protein substances of the food in the intestine, loses its harmful action with regard to the other ferments. The secretion of the above-mentioned special intestinal ferment by the wall of the intestine is solely due to the stimulating action of the pancreatic protein ferment.
Thus, the purposeful relationship of phenomena is based on the specificity of the stimuli, that correspond to similarly specific reactions. But this by no means exhausts the subject. Now the following question should be raised: how does the given property of the object, the given stimulant, reach the glandular tissue itself, its cellular elements? The system of the organism, of its countless parts, is united into a single entity in two ways: by means of a specific tissue which exists solely for the purpose of maintaining interrelations, that is, the nervous tissue, and by means of body fluids bathing all body elements. These same intermediaries transmit our stimuli to the glandular tissue. We have thoroughly studied the first kind of these interrelations.
Long before us it was established that the work of the salivary glands is regulated by a complex nervous apparatus. The endings of the centripetal sensory nerves are stimulated in the oral cavity by different stimuli; these are transmitted via these nerves to the central nervous system and thence, with the help of special centrifugal, secretory nerve fibres directly connected with the glandular cells, they reach the secretory elements and induce them to certain activity. As is known, this process, as a whole, is designated as a reflex or a reflex stimulation.
We have asserted, and also proven experimentally, that normally this reflex is always of a specific nature, i.e. that the endings of the centripetal nerves receiving the stimulation are different, each bringing about a reflex only when there are very defined external stimuli. Accordingly, the stimuli reaching the glandular cell must also be a special, peculiar one. This is the fundamental mechanism of the work of the organs purposefully depending on external influences, a relationship that is accomplished by the nervous system.
As was to be expected, the discovery of the nervous apparatus of the salivary glands immediately impelled physiologists to seek a similar apparatus in other glands lying deeper in the digestive canal. Despite great efforts no positive results could be achieved in this respect for a long time. Apparently, the new objects of investigation had essential properties that made their elucidation difficult for investigators using the earlier methods.
Taking into account these special relations, we were able, fortunately, to achieve what for such a long time had been a pium desiderium. Physiology has, at last, gained control over the nerves which stimulate the gastric glands and the pancreas. Our success was mainly due to the fact that we stimulated the nerves of animals that easily stood on their own feet and were not subjected to any painful stimulus either during or immediately before stimulation of their nerves.
Our experiments not only proved the existence of a nervous apparatus in the above-mentioned glands, but also disclosed some facts clearly showing the participation of these nerves in normal activity. Here is a striking example.
On dogs we performed two simple operations they very easily endure and after which, if taken good care of, they live for many years like very healthy and normal animals. These operations are the following: (1) Severing the tube leading from the mouth into the stomach and suturing both ends separately to the skin of the throat in such a way that food cannot pass from the mouth into the stomach of the animal but falls out through the upper opening of the tube; (2) the operation mentioned already earlier and used since a long time, in which a metal tube is introduced into the stomach through the abdominal wall. These animals have to be fed, of course, by putting the food directly into the stomach through this metal tube. When, after a fast of several hours and after the empty stomach of the dog has been thoroughly washed, the animal is fed in the natural way (whereby the food, as already mentioned, falls out of the oesophagus before reaching the stomach) then in a few minutes pure gastric juice begins to trickle out of the empty stomach. This secretion lasts as long as the animal is given food and persists some time (in a few cases even a long time) after the so-called sham feeding is discontinued. The secretion of juice is very abundant; one can obtain many hundreds of cubic centimetres of gastric juice in this way. In our laboratory we perform this operation on many dogs and the gastric juice thus obtained not only serves the purpose of research, but also as a good remedy in treating patients suffering from insufficiency of the gastric glands. Our animals living many years (more than 7-8 years) without ever showing any deviation from normal health thus donate a part of their vital supplies to the benefit of man.
From the described experiment it is clear that the mere act of eating, the food even not reaching the stomach, determines the stimulation of the gastric glands. If the so-called vagus nerves are severed at the neck of these dogs the sham feeding will no longer cause any secretion of gastric juice, no matter how long the dog stays alive and in spite of the fact that it feels excellent. So the stimulation effected by the act of eating reaches the gastric glands by means of the nerve fibres that are contained in the vagus nerves.
Now I shall allow myself to leave my main theme for a moment. Cutting of the vagus nerves in animals has been performed already for a long time and presented an absolutely fatal operation. In the course of the 19th century physiologists learned about numerous influences exerted by the vagus nerves on the different organs and their respective investigations revealed at least four disorders in the organism occurring after severing these nerves, each of which being lethal by itself. In our dogs we took appropriate measures against each of these disorders, one of which concerns the digestive system, and due to this procedure the animals whose vagus nerves were cut enjoyed a healthy and happy life. Thus, four simultaneously acting lethal causes were deliberately eliminated. A striking proof of the power of science that regards the organism as a machine!
Some ten years ago the great man to whom the annual science festival in Stockholm owes its existence honoured me and my friend, the late Professor Nencki, with a letter enclosing a considerable donation for the benefit of the laboratories under our direction. In that letter Alfred Nobel expressed his keen interest in physiological experiments and proposed that we should try several highly instructive projects concerning the supreme tasks of physiology, the problem of the organisms ageing and dying off. Indeed physiology is qualified to hope for significant victories in this field; it is as yet impossible to delimitate here the boundaries of the power of physiology. This power of physiology, however, can only be secured in the future if we continue deepening our knowledge of the organism as a very complicated mechanism. Above I have provided a small example supporting this.
I shall now return to the subject of my lecture. One kind of stimulators of the digestive glands - it quite unexpectedly came to the fore during our investigations - has not yet been mentioned. It has long been known for sure that the sight of tasty food makes a hungry man's mouth water; also lack of appetite has always been regarded as an undesirable phenomenon, from which one might conclude that appetite is essentially linked with the process of digestion. In physiology too psychical stimulation of both the salivary and the gastric glands has been reported. It is remarkable that nevertheless psychical stimulation of the gastric glands is far from being generally admitted and the outstanding role of psychical influences on the mechanism of the processing of food in the digestive tract has not at all met with proper acknowledgement. Our investigations led us to bringing these influences to the fore. Appetite, craving for food, is a constant and powerful stimulator of the gastric glands. There is not a dog in which skilful teasing with food does not evoke a more or less considerable secretion of juice from the empty and hitherto inactive stomach. At the mere sight of food nervous and excitable animals secrete several hundred, sedate and quiet animals only a few cubic centimetres of gastric juice. By modifying the experiment in a certain way an extremely profuse secretion of juice takes place in all animals without exception; I have in mind the experimental sham feeding mentioned previously in which the food cannot reach the stomach from the mouth. An exact and frequently repeated analysis of this experiment convinced us that in this case the secretion of juice cannot be regarded as being the result of a simple reflex stimulation of the mouth and throat by the food swallowed. Any given chemical irritant can be brought into the mouth of a dog thus operated upon, without even a single drop of gastric juice flowing upon this stimulation. One can still assume that the oral surface is stimulated not by arbitrary chemical substances but only by specific ones contained in the food consumed. Further observations, however, do not confirm this supposition. One and the same food acts differently as a gland stimulator depending on whether the food was consumed by the dog eagerly or unwillingly, by order. Generally the following invariable phenomenon is observed: each kind of food ingested by the dog during this experiment acts as a strong stimulus only when it suits the dog's taste. We must admit that in the act of eating the craving for food, the appetite - and therefore a psychical phenomenon - serves as a powerful and constant stimulus. The physiological significance of this juice, which we termed appetite juice, proved outstandingly great. When we introduce bread into the dog's stomach through the metal tube so as to prevent the dog from noticing it, i.e., without arousing its appetite, the bread may remain in the stomach unchanged for a whole hour, without evoking even the slightest secretion of juice, since it lacks the substances that would stimulate the gastric glands. However, when the same bread is consumed by the animal, the gastric juice secreted thereupon, the appetite juice, acts chemically on the protein substances of the bread, or, in other, more usual words, digests it. Amongst the substances resulting from the protein thus changed are some that in turn act on the gastric glands as independent stimuli. They carry on the work which is started by the first stimulus, the appetite, that naturally is diminishing by then. Already while studying the action of the gastric glands it could be discovered that appetite not only generally acts as a stimulus on these glands, but also that it excites them in a varying degree according to its direction. For the salivary glands the rule holds that all variations in their activity observed in physiological experiments are exactly duplicated in experiments using psychical stimulation, i.e. in which a given object is not brought into direct contact with the mucous membrane of the mouth, but arouses the animal's attention from some distance. For example, the sight of dry bread evokes a stronger secretion of saliva than the sight of meat, although the latter, judging from the animal's movements, may arouse a considerably keener interest. On teasing the dog with meat or any other edible substance a highly concentrated saliva flows from the submaxillary glands; the sight of distasteful substances, on the other hand, conditions the secretion of a very fluid saliva from the same glands. In short, the experiments with psychical stimulation represent an exact but reduced copy of those with physiological stimulation of the glands using the same substances. With regard to the action of the salivary glands psychology has thus taken its place besides physiology. Even more than that! At first sight the psychological aspect of this action seems to be even more indisputable than the physiological. When an object attracting the dog's attention at a distance brings about secretion of saliva, it is fully justified, of course, to assume that this is a psychical phenomenon and not a physiological one.
When, however, the dog consumes something or when a substance is forcibly poured into its mouth and saliva thereupon flows, it still has to be proved that indeed there is something physiological in this phenomenon and that it is not purely psychical but in dimensions reinforced due to special accompanying conditions. These considerations would all the more be in accordance with reality, since most substances entering the mouth while eating or artificially, strangely enough, activate the salivary glands after severing of all sensory nerves of the tongue in a very similar way as before this operation. One would have to go further, resort to more radical measures such as poisoning the animal or taking away higher parts of the central nervous system, in order to become convinced that between objects stimulating the oral cavity and the salivary glands not only a psychical but also a physiological connection exists. We are thus confronted with two series of apparently entirely different phenomena. What now is the physiologist to do with the psychical phenomena? Disregarding them is impossible since in the action of the salivary glands, in which we are interested, they are closely connected with the purely physiological phenomena. If, nevertheless, the physiologist wants to study them, he finds himself faced with the question: How?
Since we used the studies of the lowly organized representatives of the animal kingdom as an example, and, naturally, wanted to remain physiologists instead of becoming psychologists, we decided to take an entirely objective point of view also towards the psychical phenomena in our experiments with animals. Above all, we tried to discipline sternly our way of thinking and our words and ignored completely the mental state of the animal; we restricted our work to careful observation and exact formulation of the influence exerted by distant objects on the secretion of the salivary glands. The results were according to our expectations: the observable relations between external phenomena and variations in the activity of glands could be systematically analysed; they appeared to be determined by laws, because they could be reproduced at will. We were pleased to find that our experiments proved to be right and fruitful. I shall give some examples here illustrating the results obtained with the new method in our field of interest.
When the dog is repeatedly teased with the sight of objects inducing salivary secretion from a distance, the reaction of the salivary glands grows weaker and weaker and finally drops to zero. The shorter the intervals between repeated stimulations the quicker the reaction reaches zero, and vice versa. These rules apply fully only when the conditions of the experiment are kept unchanged. The identity of the conditions, however, need to be only of a relative character; it may be restricted only to those phenomena in the external world that were previously associated with the act of eating or with the compulsory introduction of the substances in question into the animal's mouth; the variation of the remaining phenomena is of no significance. This relative identity mentioned above can be very easily attained by the experimenter so that an experiment in which a stimulus repeatedly applied from a distance gradually loses its effect, can be readily demonstrated even in the course of one lecture. When in a repeated stimulation from a distance a certain substance becomes ineffective, the action of another substance is not at all eliminated. For example, when milk ceases to produce an effect, the action of bread is very strong. When bread too has lost its effect due to repetition of the stimulation experiment, acid or other substances is still highly effective. These relations also explain the real meaning of the above-mentioned identity of experimental conditions; every detail of the surrounding objects appears to be a new stimulus. If a certain stimulus has lost its influence, it can recover the latter only after a long resting that has to last several hours.
The lost action, however, can also be restored with certainty at any time by special measures.
When repeatedly showing of bread no longer stimulates the dog's salivary glands one needs only to let the animal eat bread to attain full restoration of the action of bread at a distance. The same result is achieved when the dog is given some other food. Even stronger: If something inducing salivary secretion, such as acid, is brought into the animal's mouth, the original action of the sight of bread is also restored. Generally, everything that stimulates the activity of the salivary gland retrieves the lost reaction: the greater the activity the more fully the reaction is restored.
Also according to rules our reaction can be inhibited by certain interferences, for instance, affecting the dog, its eye or its ear by an extraordinary stimulus and thereby evoking a strong motor reaction in the animal such as trembling of the entire body.
Since my time is limited I shall content myself with what I have said and pass on to the theoretical consideration of the experiments just mentioned. The given facts fit readily in our physiological way of thinking. Our stimuli working from a distance may rightly be termed and regarded as reflexes. When observing carefully it appears that the activity of the salivary gland is always excited by some external phenomenon, i.e. that it is induced by external stimuli like the usual physiological salivary reflex; only the second is evoked from the oral surface, the first, however, from the eye or from the nose, etc. The difference between the two reflexes is firstly that our old physiological reflex is constant, unconditioned, while the new reflex continually fluctuates and, hence, is conditioned. Examining the phenomena more closely the following essential differences between the two reflexes can be observed: in the unconditioned reflex those properties of the object act as stimuli with which the saliva is confronted physiologically e.g. hardness, dryness, certain chemical properties; in the conditioned reflex, however, those properties of the object act as stimuli that in themselves have no direct relation at all with the physiological role of the saliva, e.g. colour, etc. These last properties appear here in some way as signals for the first. One is bound to regard their stimulating action as a further, more delicate adaptation of the salivary glands to the phenomena in the external world. Here is an example: We intend to pour acid into the dog's mouth; to protect the oral mucous membrane it is apparently very desirable that saliva accumulates before the acid enters the mouth; on the one hand the saliva prevents direct contact of the acid with the mucous membrane and, on the other hand, it immediately dilutes the acid thus generally weakening its injurious chemical action. However, essentially the signals have only a conditional significance: they change readily and also, the signalized object cannot come into contact with the oral mucous membrane. Consequently the finer adaptation would have to consist in the fact that the properties of the object serving as a signal sometimes do and at other times do not stimulate the salivary glands. This is what we see in reality. Any phenomenon in the external world can be made a temporary signal of an object stimulating the salivary glands, if the stimulation of the oral mucous membrane by this object has been associated repeatedly once or several times with the action of the given external phenomenon on other sensitive body surfaces. In our laboratory we are trying at present to apply many such highly paradoxical combinations, and with success. On the other hand promptly active signals can lose their stimulating effect if repeated over a long period without bringing the object concerned into contact with the oral mucous membrane. When the most usual kinds of food are shown to the dog for days and weeks, without letting him eat it, the sight of the food will finally cease to evoke salivary secretion. The mechanism of stimulating the salivary glands through the signalling characteristics of the objects, i.e. the mechanism of "conditioned stimulation" can be easily conceived from the physiological point of view as a function of the nervous system. As we have just seen, each conditioned reflex, i.e. stimulation through the signalling characteristics of the objects is based on an unconditioned reflex, that is, a stimulation through the essential characteristics of the object. So it must be assumed that the point of the central nervous system that is being stimulated strongly during an unconditioned reflex diverts to itself the weaker stimuli exerted by the external world on other points of the central nervous system, i.e. that due to the unconditioned reflex a temporary, incidental path is created for all the other external stimuli towards the central point of this reflex. The conditions influencing the opening and closing of this path, its being in use or in disuse, constitute the internal mechanism of the signalling characteristics of external objects being effective or ineffective, the physiological basis of the finest reactivity of the living matter, the most delicate adaptive capability of the animal organism.
I wish to express here my deep conviction that in this direction, along the broad lines I have sketched, physiological research can advance greatly and successfully.
Essentially only one thing in life interests us: our psychical constitution, the mechanism of which was and is wrapped in darkness. All human resources, art, religion, literature, philosophy and historical sciences, all of them join in bringing light in this darkness. But man has still another powerful resource: natural science with its strictly objective methods. This science, as we all know, is making huge progress every day. The facts and considerations which I have placed before you at the end of my lecture are one out of numerous attempts to employ a consistent, purely scientific method of thinking in the study of the mechanism of the highest manifestations of life in the dog, the representative of the animal kingdom that is man's best friend. 巴甫洛夫对条件反射的解释
巴甫洛夫是一个生理学家，他对条件反射的解释是大脑皮层内进行的一种生理过程，建立了以高级神经活动为基础的条件反射理论。
1.条件反射的中枢神经机制
条件反射是条件刺激在中枢神经引起的兴奋与无条件刺激引起的兴奋之间形成暂时性神经联系的结果。联系可以说是由时间顺序和相对强度决定的。时间顺序一般是条件刺激先到来，起着信号的作用。相对强度是指通常具有较强兴奋的无条件刺激吸引着来自条件刺激中心的兴奋。
2.高级神经的活动
巴甫洛夫认为，高级神经活动有两个基本的过程：兴奋和抑制。它们的相互作用是大脑两半球活动的基础。兴奋过程是指兴奋由某一特定的细胞群扩散到整个皮层区的其他不同细胞群。这种扩散就是泛化的生理基础。
在分化训练期间，兴奋的集中抑制兴奋的扩散，条件刺激得到强化，相似刺激得不到强化，通过这种辨别的分化作用，形成对相似刺激的抑制过程，这样就减缩了条件刺激的兴奋扩散，使之集中在原来的地方。
当兴奋和抑制都集中时，便发生相互诱导。在相互诱导中，在集中的抑制刺激之后运用条件刺激，条件刺激的反应就会变得更强；同样，在集中的条件刺激之后出现抑制性刺激时，抑制性刺激的效应就会变得更强。所以，大脑皮层的活动是由兴奋与抑制通过扩散，集中，相互诱导的交互作用完成的。
3.神经系统的类型
巴甫洛夫根据兴奋与抑制的强弱，转换快慢，是否平衡将神经系统划分成四种类型：多血质，胆汁质，粘液质，抑郁质。
4.两种信号系统
巴甫洛夫提出了人所特有的第二信号系统。第二信号系统是人类对语言形成条件反射的信号系统。巴甫洛夫第二信号系统的提出，说明他对语言的作用已有了认识，但他没有从实验上或理论上发展这些思想。
（四）经典条件作用与工具条件作用
现今心理学界普遍认为有两种条件反射：一是巴甫洛夫的经典性条件反射；二是斯金纳的操作性条件反射。两种条件反射的主要区别有：1）程序的安排不同。在操作性条件反射中，US的提供不依赖于被试是否对条件刺激（CS）做出反应；而在工具性条件反射中，对一次尝试的强化依赖于关键性的反应是否发生。2）条件反应不同。在操作性条件反射中，条件反应通常是由US引起的无条件反应的一部分或者彼此有相似之处；在工具性条件反应中，操作反应通常与无条件刺激的反应无相似之处，如，压杠杆与进食，唾液分泌。3）可操作的内在变量不同。在经典性条件反射中，条件刺激与无条件刺激的时间间隔是内在变量，而在工具性条件反射中，内在变量则是反应至强化的时间间隔。4）有的理论家认为，两种条件反应的反应系统不同。操作性条件反射是以植物性神经的平滑肌（如心脏与腺体）为中介物，反应是不随意的；而工具性条件反射则以大型的平滑肌（如四肢）为中介物，反应是随意的。 巴甫洛夫的弟弟—一百年前的人体生物实验牺牲品
巴甫洛夫通过实验发现了条件反射的原理，这为他赢得了国际声誉。在他最著名的实验中，他通过训练，让狗听到铃铛的声音就不由自主地大量分泌唾液。但很少有人知道，他曾经在自己亲弟弟身上做过类似的实验。这次实验的具体细节刚刚被披露，实验本身以及它悲剧性的进展进一步激化了人们对在动物或自己亲属身上进行科学实验伦理问题的争论，反对进行人体克隆实验的人们也开始以此作为例证。
1903年春季的一天，巴甫洛夫和父母、弟弟一起参加一次午宴。弟弟尼古拉是一个帽子设计师，但当时正失业在家。兄弟俩感情并不好，弟弟对大名鼎鼎的学者哥哥已经由嫉妒演变成赤裸裸的厌恶。午宴上，巴甫洛夫说起他正在进行的研究，说要在狗身上进行唾液分泌的条件反射实验。当时，他正觉得弟弟喝红菜汤的“呼噜”声无法忍受，所以恶狠狠地把“狗”说成了“脏狗”。还没等他说完自己的计划，妈妈打断了他。
“你和那些混蛋一起研究还不如找你的弟弟和你一起去，你弟弟最馋嘴了，谁的口水也没有他多。”
“妈妈，我知道自己该怎么工作。”巴甫洛夫回答道。
“但是你的决定会让你失业的弟弟继续闲在家里，而把工作机会让给那些你甚至根本不认识的脏狗！”
面对夹杂不清的母亲，巴甫洛夫只好向父亲投去求助的目光。但这个可怜的老实人已经和夫人共同度过了太长的岁月，他的脸上是和往常一样顺从的谄媚微笑。“我觉得这主意挺好，你们兄弟俩正好可以多花点时间在一起，在工作中还可以互相帮助。”
老两口的好意显然没有任何效果，踏入实验室的大门，兄弟俩就气呼呼地对视着，助手们都看得出他们之间已经仅剩下憎恨，丝毫没有一点兄弟的情谊了。尼古拉不想被当作一只小白鼠，但巴甫洛夫觉得他连一个合格的实验动物都算不上，连一条狗都不如。
在选一个能让尼古拉有食欲、流口水的盘子时，他们就吵得不可开交。然后，在讨论选什么食物作为实验的辅助材料时，他们再一次争吵起来。尼古拉坚持说除了上好的鱼子酱，别的东西不能让他马上流口水。巴甫洛夫气炸了肺，他生气地说，科学家的研究是为了崇高的理想，不是为了赚钱，他自己都吃不起鱼子酱，怎么能拿这么贵重的东西喂“狗”。争吵了几天，鱼子酱飞出了实验室，取而代之的是烤面包片。
实验开始的头两天，巴甫洛夫一次又一次地先摇响铃铛，然后给弟弟一盘面包片。他在实验日志中写道：“我弟弟就像屁股上的脓包一样让人讨厌，但不可否认的是，他分泌唾液的反射非常好，是个合适的实验品。”
但在第三天，意外发生了。巴甫洛夫像往常一样摇动铃铛，但却没有拿出面包片。尼古拉的反应并不是止不住地流口水，而是抡圆了胳膊，打得哥哥鼻血长流，把巴甫洛夫打进了医院。
母亲到医院看望儿子，但丝毫没有同情的意思。“你在搞什么狗屁实验，摇了铃铛但不给尼古拉吃的，”她质问道，“你知道你弟弟肚子饿的时候就像个疯子一样。”
巴甫洛夫躺在医院里，尼古拉可没闲着。他流连于圣彼得堡的各个酒吧和咖啡屋，随便逮着一个人，就跟他说“自己”进行的实验多么令人惊奇。尼古拉的夸夸其谈达到了顶峰，他在接受《圣彼得德堡日报》周末版的采访时，让自己完全替代了巴甫洛夫在实验室里的地位。“他只是我的书记员”，他对记者们吹嘘道，“我才是整个实验的指导者，我在仔细地流口水的时候他就知道在一边傻呵呵地摇铃铛。”在病床上读到这篇报道，巴甫洛夫再也忍受不住了，他不顾还打着石膏的鼻子，重新回到了实验室。
这次，巴甫洛夫找了一只公牧羊犬代替自己的弟弟。实验者和实验品终于不用再说话，兄弟俩也再没有说过话，只有一次巴甫洛夫收到一封辱骂自己的电报，他觉得这是弟弟发的。
在获得诺贝尔奖的致谢辞中，他感谢了上帝、他的助手们，还有那只牧羊犬，但没有提及尼古拉。
尼古拉折腾了一阵后，渐渐在人们的视野里消失了。他后来进入圣彼得堡的橡皮厂当会计。那些曾经听说过他辉煌的过去、并一直到他平庸的晚年还认识他的人，都承认在他身上丝毫找不到曾经扮演过科学史上如此重要角色的印记，当然，在电话铃声响起的时候除外。 介绍巴甫洛夫的研究的一个文件已经上传到：
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