GENERAL ORGANOLOGY. 1 2/ 



the ectoderm ; in vertebrates, on the contrary, the ectoder- 

 mal gut areas are extremely short. 



The width of the lumen varies in the course of the 

 alimentary canal and renders possible the distinction of 

 different divisions, which in the animal series have been 

 provided, so far as possible, with uniform names. Fig. 

 57, drawn from a domestic fowl, may serve for explana- 

 tion of the usual terms. The mouth-opening leads into 

 a wider cavity, which is usually divided into an anterior 

 division, the buccal cavity , and a posterior one, \h& pharynx. 

 The narrow tube leading from this is the oesophagus (a] ; 

 here and there it may w^iden, or bear a pouchlike evagina- 

 tion, the crop or ingluvics ($), for the temporary reception 

 of food. From the oesophagus, the food passes into a 

 considerable enlargement, the stomach. Birds, like many 

 other animals, have a double stomach, a thin-walled por- 

 tion rich in glands, and a second part, the walls of which 

 are remarkable for the thick masses of muscle ; the former 

 is the glandular stoinacli (<r), the latter is the grinding 

 stomach or gizzard (//), serving for comminution of the 

 food. Behind the stomach the digestive tube narrows 

 into the small intestine (/?), the hinder widened part of 

 which is the large intestine (/), terminating in the anus. 

 The limit of the small and large intestine is usually marked 

 by blind pouches, the cceca (K). Connected with the anal 

 gut also, are the outlets of the kidneys (in) and of the sex- 

 ual apparatus (;/); hence the terminal portion, serving as 

 the outlet for the urine and faeces, and also for the sexual 

 products, is called the cloaca (a). 



In animals which require a more abundant food, the 

 area of the alimentary tract is not sufficient to furnish the 

 digestive fluids, so that evaginations of the gnt-wall 

 (glands) must serve to increase this. Into the mouth 

 empty the salivary glands ; into the first part of the small 

 intestine, close behind the stomach, the liver (e) and the 

 pancreas (g] (or a simpler glandular apparatus, whose se- 

 cretion combines the characters of gall and of pancreatic 

 juice, the hepato-pancreas]. Finally, in the end-gut there 



