■64 Journal of Agriculture. [9 Dec, 1907. 



In animals that possess no proventriculus, namely in man and carni- 

 vores, the masticated food enters the fundus directly. If the amount of 

 food be great the gastric juice may not penetrate through the mass for some 

 time and so the saliva may continue to act on the starch. When however 

 the food mass is saturated with the acid juice the action of the saliva 

 on the starch is stopped. In such animals autolysis of the food practically 

 does not occur. 



Fats in the stomach are acted upon only very feebly ; but as the 

 envelopes of the fat-cells are digested, when the fat is of animal origin, 

 a liberation of the fat occurs so that it is prepared for subsequent digestion. 

 Carbohydrates are unchanged in the stomach with the exception of that 

 due to the saliva before it is acidulated. Summarising the digestive 

 processes so far we may state that in mammals food is ground and its 

 surface multiplied by the action of the teeth. In animals with a proven- 

 triculus all food constituents are slightly digested by autolysis and 

 bacterial action, but the main action is a loosening and softening of the 

 fibres and cellulose cell-walls. Complex carbohydrates (polysaccharides 

 and notably starch) are partially broken down into sugars by the action 

 of saliva and by autolysis in the crop. In the fundus of the stomach 

 proteins are saturated with acid and sul>jected to pepsin ; bv this means 

 all solid protein that is not retained within the woodv envelopes is dissolved 

 or pulped, being broken down into the simpler proteoses. 



In addition to these functions we may describe some others. The 

 proventriculus or the stomach acts as a reservoir of food so that while 

 the latter may be eaten intermittently (this is especially the case with 

 carnivores) the intestines receive a continuous supply. In most animals 

 the stomach never becomes actuallv empty and, by this reservoir action, 

 can tide the animal over short periods of starvation. Another important 

 action is the dilution of strong solutions down to a fixed concentration. 

 or converselv, of strengthening weak solutions up to the same standard. 

 Thus a syrup of sugar or a draught of Epsom salts is diluted, but pure 

 water has salts added to it. This is an important action for the delicate 

 lining membrane of the intestine is readilv disturbed by concentrations 

 above or below the standard. 



It is verv doubtful if anv absorption occurs before the small intestine is 

 reached except as regards highly diffusible bodies such as alcohol. &c. 



The glands of the stomach are stimulated into action by the advent of 

 the food. In man and carnivores gastric juice is poured out in the act 

 of eating or even at the sight or thought of food, just as the human mouth 

 will proverbiallv water at the bare mention of a lemon. But the food 

 has also a further and direct stimulating influence when it reaches the 

 stomach. In ruminants a response of the stomach before the food has 

 entered it is probably absent. 



The pylorus of the stomach is characterised by strong peristaltic waves 

 that drive the stomach contents, when these become sufficientlv pulped or 

 digested, through the pvloric sphincter into the duodenum. The glands 

 with which the pvlorus is supplied act chieflv bv adding some more pepsin 

 to the food ; thev do not add acids as the proteins have already been 

 saturated with hydrochloric acid in the fundus, 



{To he cotifiinicd .) 



