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SCIENCE. 



[N. S. Vol. XIV. No. 356. 



the department of physiology or of medi- 

 cine. To those readers of Science who are 

 not familiar with the details of modern 

 physiological investigation, a brief review 

 of the more important work of this brilliant 

 Russian investigator may be of interest. 



Professor Pawlow's researches have, for 

 the most part, been directed to the solution 

 of problems connected with the physiology 

 of secretion. His persistent efforts in this 

 field have been crowned with success to an 

 unusual degree ; and physiology owes to 

 him and his coworkers much of the prog- 

 ress which has been made in recent years 

 towards a clearer understanding of the 

 processes of digestion in the animal organ- 

 ism. New experimental methods have 

 been devised, and older ones applied to 

 new purposes. 



With reference to the nitrogenous met- 

 abolism of the salivary glands, Pawlow 

 showed (1888) by direct chemical analysis, 

 that anabolic and katabolic processes are 

 coincident in the secreting organ. This 

 observation, usually overlooked by physiol- 

 ogists, was in itself an important contri- 

 bution to the theory of secretion. The 

 extensive series of experiments on the 

 innervation of the gastric and pancreatic 

 glands — researches which have had their 

 origin in Pawlow's laboratory — have evoked 

 the widest attention. In this study of 

 gastric secretion the improvements in the 

 general technique consisted primarily in 

 the simultaneous introduction of an ordi- 

 nary gastric fistula (in dogs) and a division 

 of the oesophagus in the middle of the neck. 

 The cut ends were attached to openings in 

 the neck so that swallowed food passed 

 out at one opening without reaching the 

 stomach; and, through the other, food 

 which it was desired should enter the 

 stomach could be passed in. The more 

 important facts ascertained by the use of 

 this method were, that when food is eaten 

 a flow of gastric juice is started ; inasmuch 



as under the experimental conditions re- 

 ferred to the ingested material fails to reach 

 the stomach, the reflex character of the im- 

 pulses which provoke the secretion can 

 thus be demonstrated. The paths along 

 which the reflex stimulation reaches the 

 gastric glands were shown to be the vagus 

 nerves ; for while section of the splanchnics 

 does not interfere with the reflex secretion, 

 this reaction entirely disappears after di- 

 vision of the vagi. To make the proof 

 complete, Pawlow showed that artificial 

 stimulation of the peripheral end of a cut 

 vagus will incite a flow of active gastric juice. 



The possibility of obtaining pure gastric 

 juice uncontaminated with the products of 

 digestion was thus accomplished in a way 

 never before equaled. It remained, how- 

 ever, to observe the production of the se- 

 cretion and its properties during the course 

 of actual digestion. Heidenhain had al- 

 ready developed a method of isolating one 

 portion of the stomach from the rest, so that 

 it was possible to keep animals in this con- 

 dition under observation for a long period. 

 In his operations, however, the nerve sup- 

 ply to the isolated portion was undoubtedly 

 seriously interfered with. Pawlow im- 

 proved the method, so that there remained 

 an undisturbed nerve distribution, the func- 

 tional importance of which he clearly 

 showed. Secretion in the isolated portion 

 could thus be followed while digestion was 

 proceeding in the adjoining parts of the 

 stomach. 



Along similar lines our knowledge of the 

 work of the pancreas and the production of 

 the bile has been largely added to by Paw- 

 low and his pupils. The introduction of a 

 successful method for obtaining permanent 

 fistulas has been followed by a study of the 

 secretory activity of the pancreatic gland. 

 The reflex character of the ordinary stimuli 

 has been demonstrated, and the paths 

 through which the impulses reach the gland 

 ascertained. The existence of inhibitory 



