CHEMISTRY OF DIGESTION AND NUTRITION. 237 



just been said, they lose this property as soon as they undergo the change 

 from living to dead structure. The digestion of the living frog's leg in 

 gastric juice, and similar instances, do not affect this general idea, since, as 

 Bernard himself pointed out, what happens in this case is that the tissue is 

 first killed by the acid and then undergoes digestion. On the other hand, 

 Neumeister has shown that a living frog's leg is not digested by strong pan- 

 creatic extracts of weak alkaline reaction, since under these conditions the 

 tissues are not injured by the slightly alkaline liquid. When it is said that 

 the exemption of living tissues from self-digestion is due to the peculiarities 

 of their structure, it must not be supposed that this is equivalent to referring 

 the whole matter to the action of a mysterious vital force. On the contrary, 

 all that is meant is that the structure of living protoplasmic material is such 

 that the action of the digestive secretion is prevented, possibly because it is not 

 absorbed, this result being the outcome of the physical and chemical forces 

 exhibited by matter with this peculiar structure. While a statement of this 

 kind is not an explanation of the facts in question, and indeed amounts to a 

 confession that an explanation is not at present possible, it at least refers the 

 phenomenon to the action of known properties of matter. 



General Remarks upon the Physiology of the Stomach. From the 

 foregoing account it will be seen that, speaking generally, the functions of the 

 stomach are in part to act chemically upon the proteids, and in part, by the 

 combined action of its secretion and its muscular movements, to get the food 

 into a physical condition suitable for subsequent digestion in the intestine. 

 The material sent out from the stomach (chyme) must be quite variable in 

 composition, but physically the action of the stomach has been such as to 

 reduce it to a liquid or semi-liquid consistency. The extent of the true 

 digestive action of gastric juice on proteids is not now believed to be so 

 complete as it was formerly thought to be. Examination of the chyme 

 shows that it may contain quantities of undigested or only partially digested 

 proteid, complete digestion being effected in the intestines. Moreover, arti- 

 ficial peptic digestion of proteids under the most favorable conditions shows 

 that only a portion is ever converted to peptone, most of it remaining in the 

 proteose stage. It has been suggested, therefore, that gastric digestion of 

 proteids is largely preparatory to the more complete action of the pancreatic 

 juice, whose enzyme (trypsin) has more powerful proteolytic properties. In 

 accordance with this idea, it has been shown that an animal can live and 

 thrive without a stomach. Several cases 1 are on record in which the stomach 

 was practically removed by surgical operations, the oesophagus being stitched 

 to the duodenum. The animals did well and seemed perfectly normal. Exper- 

 iments of this character do not, of course, show that the stomach is useless in 

 digestion ; they demonstrate only that in the animals used it is not absolutely 

 essential. The reason for this will better be appreciated after the digestive 

 properties of pancreatic secretion have been studied. 



1 Ludwig and Ogata.- Archiv fur Anatomie und Physiologic, 1883, p. 89; and CarvaHo and 

 Pachon : Archives de Physiologic normale et pathologique, 1894, p. 106. 



