INTESTINAL SYSTEM 217 



Potassium sulpho-cyanide, which occurs in small varying per- 

 centage in human saliva, is not peculiar to man, for although 

 it is not found in horses, oxen, sheep, pigs and goats, it is pre- 

 sent in the saliva of dogs. 



As regards gastric digestion, man resembles those animals 

 that eat flesh either exclusively, or in part, in so far as he has 

 a simple stomach as opposed to the compound stomach of 

 ruminants. The stomach of the equidae is single but 

 relatively of much less capacity ; only the right half can be 

 reckoned as true stomach mucosa, for the left half does not 

 possess glandular tissue. In this respect there is a great 

 similarity between the gastric digestion of man and the omni- 

 vora, since two stages can be distinguished, a short first stage 

 in the left segment for the after- working of the swallowed 

 saliva, and a second stage in which the hydrochloric acid and 

 pepsin act. 



The chemical factor of digestion plays its part in the fundus, 

 the mechanical in the pyloric antrum. 



The specific gravity of the gastric juice is : 



In man . . roo22- 1*0024 



mammals . . . rooi-roio 



As to the amount of solid constituents of the gastric juice man 

 ranks lowest with i'2OO per cent, as compared with the i'385 

 per cent, of sheep and the 2*69 per cent, of dogs. 



The detailed quantitative analysis agrees with this, for in 

 the case of man, in addition to 994/4 of water, 2*41 inorganic 

 material, and 0*2 HC1, there is only 3*19 of organic substances, 

 while the herbivorous sheep yields 4*05, the horse 9'8, and the 

 carnivorous dog 17*33 ( tne total amount is reckoned as looo). 1 



The motor nerve to the stomach is the vagus ; if this nerve 

 is divided, and the peripheral end stimulated in a recently fed 

 animal a vigorous peristalsis is induced, and this passes down 

 the small intestine. With division of the vagus the so-called 

 psychical secretion of gastric juice ceases (" appetitsaft "), but 

 not the reflex secretion, which justifies the assumption that 

 the latter depends on sympathetic-fibres running with the 

 vagus. 



1 Ellenberger, loc. cit., ii., p. 515. 



