DIGESTION OP POOD. 



279 



r\ 





^-'■ 



large part in the actual preparation of the food for absorption, 

 ^-^^d these lie, of course, the vital properties of the glands, 

 jare the active fluids from 



so that a study of diges- 



Hy divides itself into the 



in of — 1. The digestive 



Che secretory processes; 

 muscular and nervous 

 by which the food is 



a one part of the digest- 

 another, and the waste 



Ily expelled. 



.OgicaL — The alimentary 



have seen, is formed by 



f of the splanchnopleure, 



hng as the growth is 



i marked, does the canal 



tuous or remain some- 



at. The alimentary tract 

 of a mammal passes through stages 

 of development which correspond with the permanent form of 

 other groups of vertebrates, according to a general law of evo- 

 lution. Inasmuch as the embryonic gut is formed of mesoblast 



Fig, 



canal of 



,in of alimentary 

 ick at fourth day 



(Foster and Balfonr, after GOt- 

 te). tg, diverticulum of one 

 lung; St, stomacli; I, liver; p, 

 pancreas. 



Fio. 227. — Position of various parts of alimentary canal at different stages. A. Em- 

 bryo of five weeks. B. Or eight weeks. C. Of ten weeks (Allen Thomson). I, 

 pharynx with the lungs; 8, stomach; i, small intestine; i', large intestine; g, geni- 

 tal duct; u, bladder: cl, cloaca; c, csecam; vi, ductus vitello-intestinalis; si, uro- 

 genital sinus; v, yelk-sac. 



