130 A Manual of Veterinary Physiology. 



periods, the existence of which has been determined by 

 Ellenberger and Hofmeister, whose views are here given : 



First period : lasts but a short time, during which starch is 

 converted into sugar, accompanied by lactic fermentation. 



Second period : during this starch is principally converted 

 into sugar in the left sac, and a small quantity of proteid is 

 converted into peptone in the fundus ; the acids present 

 are lactic in the left, and a little hydrochloric in the right 

 sac. 



Third period : one of mixed digestion ; both starch and 

 proteid conversion occurs — the former in the pylorus, the 

 latter in both fundus and pylorus. The acid present is 

 principally hydrochloric. 



Fourth period consists of pure proteid digestion ; no starch 

 conversion can occur owing to the universal presence of 

 hydrochloric acid. It is impossible to state definitely the 

 length of these various periods, for so much depends upon 

 the presence of fresh food in the stomach. Where the 

 interval between the meals is considerable, the periods 

 extend over several hours ; and in all cases they run into 

 one another. Had it not been for the Aveight of Ellen- 

 berger's authority, I should not have considered it necessary 

 to have mentioned the various periods given above. 



After a moderate feed digestion is at its height in 3 or 4 hour*. 

 „ full „ „ ,, „ 6 to 8 „ 



„ an immoderate „ ,, delayed still longer. 



Gastric Digestion of Ruminants. — Ruminants are described 

 as having four stomachs — viz., the rumen, reticulum, 

 omasum, and abomasum. Physiologically considered, there 

 is but one stomach — viz., the abomasum ; the others may 

 be regarded as (esophageal dilatations. 



The Rumen is of enormous size, capable of holding 

 GO gallons ; it is divided into certain sacs, has a well- 

 developed mucous membrane, which in part is covered by 

 leaf-like papilla 1 , the glands are small and unimportant, 

 and contribute no digestive fluid. The muscular fibres of 

 the wall are distinctly striated, which is a remarkable 



