Digestion. 133 



regurgitation from the fourth stomach. The third stomach 

 has a separate source of nerve supply. Irritation of the 

 pneumogastric produces contraction of all the other stomachs 

 but this one. 



In the Abomasum, or fourth stomach, true digestive 

 changes occur. The acid secretion, formed in the manner 

 before described, converts the proteids into peptones, this 

 change being more active at the cardia than at the pylorus. 

 Ellenberger states that in the abomasum the digestion of 

 starch is the first to take place, and then proteid digestion. 



In the fourth stomach of the calf a milk-curdling ferment 

 exists. 



Stomach digestion in the Pig has also been worked out 

 by Ellenberger and Hofmeister. The stomach of the pig is 

 peculiar ; it is a type between the carnivorous and ruminant, 

 and is divided by the above observers into live distinct 

 regions, which do not all possess the same digestive activity. 



The gastric juice of the pig contains for the first hour or 

 two of digestion lactic, and afterwards hydrochloric, acid ; 

 pepsin is present, and a ferment which converts starch into 

 sugar. 



The remaining points in gastric digestion in the pig, viz., 

 the various periods of digestion, the changes in the acid, 

 and the slowness with which the viscus empties itself when 

 no fresh food is given, are identical, strange to say, with 

 those of the horse. 



Absorption from the Stomach.— The needful changes having 

 occurred in the stomach, and I now refer principally to the 

 stomach of the horse, our next step is to inquire into the 

 proportion of food so altered as to be fit for absorption. 



Experiment shows that in the stomach 40 to 50 per cent, 

 of the carbo-hydrates of the food have been converted into 

 sugar ; whilst 40 to 70 per cent, of the proteids are con- 

 verted into peptones. Where food has been long in the 

 stomach, not more than 2 to 10 per cent, of the proteids 

 pass out unacted upon ; but under ordinary circumstances 

 we cannot count upon a larger digestion of proteids than 

 40 per cent. 



