lO 



NATURE 



[March 2, 1916 



vitsch, in Petrograd, and in it he showed that a 

 reflex constriction of the blood vessels of the ear 

 of the rabbit occurs on opening- the abdominal 

 cavity. This was extended in 1879 to reflex 

 eff'ects on blood pressure due to variations in the 

 distension of the stomach before and after section 

 of the vagus nerve. His work, in fact, at this 

 time and for more than fifteen years later was all 

 concerned with .innervation mechanisms. 



In 1878 he studied the nervous mechanism of 

 pancreatic secretion. This, though vitiated by 

 overlooking certain factors which have since come 

 to light, largely through the investigations of his 

 own pupils, was of a most painstaking character 

 and appeared to bring the secretory mechanism 

 of the gland into line with that of other similar 

 organs. As an outcome of it, he introduced an 

 important improvement in the making of pan- 

 creatic fistulae for the study of the outflow of the 

 juice, the principle of which he extended (1883) 

 to the collection of urine from the urinary bladder. 



Up to this time Pavlov remained in Petrograd, 

 but in 1884 he went to Breslau, and there under 

 Heidenhain carried out work- — also in the domain 

 of the nervous system — namely, an investigation 

 into the neuro-muscular mechanism of the open- 

 ing and closure of the valves of the mussel. In 

 1886 he went to Leipzig to study under Ludwig, 

 and from there published an article on the nervous 

 control of the left ventricle of the heart. 



This was followed in 1887 by an elaborate piece 

 of work from Botkin's laboratory, Petrograd, 

 which showed great thoroughness and insight, 

 namely, on the centrifugal nerves of the heart. 

 His conclusions were that there are four classes of 

 such nerves — inhibiting of frequency, inhibiting 

 of force, augmenting of frequency, and augment- 

 ing of force of the heart's contractions. This 

 work may be said to mark the close of the first 

 period of his activities. The succeeding fourteen 

 years were devoted to his main life-work — a study 

 of the activities of the digestive glands. In 1888 

 a further contribution to the secretion and inner- 

 vation of the pancreas appeared, followed in 1889 

 and 1890 by articles, in conjunction with Madame 

 Schumova-Simonovskaja, on the innervation of 

 the glands of the stomach. These indubitably 

 established the fact that the secretion of gastric 

 juice is directly controlled by the vagus nerve. 

 The difficulties met and surmounted in this 

 investigation can only be adequately gauged when 

 it is remembered that six years earlier, Heidenhain 

 had written in Hermann's great text-book of 

 physiology as follows: — "The results of the 

 numerous observations quoted proclaim, without 

 doubt, that the extrinsic nerves of the stomach 

 possess no demonstrable influence, of a direct 

 kind, on its secretion" (Hermann, "Handbuch," 

 Ed. v., I, S. 121, 1883). Numerous colleagues 

 and pupils from this time began to associate 

 themselves with Pavlov, amongst them being 

 M. Nencki, an able biological chemist. To this 

 co-operation is to be attributed work on the 

 ammonia content of the portal and other veins in 

 its relation to the formation of urea by the liver. 



NO. 2418, VOL. 97] 



Pavlov's technical skill was here shown in the 

 success with which he performed the diflicult 

 operation of establishing the communication 

 between the portal vein and the inferior vena 

 cava, known as Eck's fistula. 



About this time an occurrence took place which 

 greatly influenced the master's later career. In 

 1885, a short time after Pasteur had discovered 

 his method of treating hydrophobia, an officer of 

 the regiment of the Guards lost his life through 

 the bite of a rabid dog. Prince Alexander Petro- 

 vitch, of Oldenburg, who commanded the corps 

 of the Guards at that time, was so affected by 

 the sad event that he established at his own 

 expense a laboratory for the treatment of the 

 disease in the infirmary of the regiment. The 

 work of this laboratory grew ; investigations were 

 undertaken, as well as treatment applied, and in 

 18.88 the Prince obtained permission from the 

 Emperor to found an institution for the experi- 

 mental study of medicine. A site was chosen in 

 the outskirts of Petrograd in a beautiful park 

 adjoining the Neva, and in April, 1891, the 

 Imperial Institute of Experimental Medicine was 

 opened by order of the Czar, with Prince 

 Alexander of Oldenburg as curator. Regular work 

 began in the following October. The institute 

 comprised numerous buildings and laboratories^ 

 and embraced six sections, namely, physiology, 

 pathological anatomy, biological chemistry, bac- 

 teriology, epizootology, and syphilidology. Pavlov 

 was chosen to be chief of the section of physio- 

 logy, and Nencki that of biological chemistry. 



Here under ideal conditions, with numerous 

 colleagues and a large staff of assistants, Pavlov 

 continued, his investigations for the remainder of 

 his life. The earlier work of the institute was 

 published in Russian and French in the Archives 

 des Science Biologique de St. Petershourg, and 

 a summary of it was given in 1897 by Pavlov in 

 a series of lectures to Russian medical men, which 

 was published in Russian. A German translation- 

 appeared in 1898, followed by French and English 

 translations in the next few years. It was mainly 

 through these that European and other physio- 

 logists outside Russia, came fully to recognise the 

 j importance of the work carried on in Petrograd. 

 j It is not too much to say that all were profoundly 

 I impressed. Pavlov had for the first time devised 

 methods of obtaining all the impnartant digestive 

 secretions, in pure condition, in exactly measur- 

 able quantities, and from animals in perfect 

 health. 



In his studies on the secretion of gastric juice 

 Pavlov became impressed with the importance of 

 the psychic stimulus, produced by the taste,, 

 sight, and smell of food. This was further showR 

 in the secretion of saliva, where not only the 

 flow, but the com|X)sition of the saliva was in- 

 fluenced in this way. Thus dry food caused a 

 copious flow of thin, watery saliva ; moist food a 

 scanty flow of viscid saliva. The former was- ! 

 needed for the chewing of food, the latter only to- i 

 facilitate swallowing. In these results he recog- 

 nised the great effect of external, possibly un- 



