YERTEBRATA. 



179 



of the body ; in the sheep its proportionate length is as 28 to 

 I, whilst in the carnivora the proportion is about 4 to 1. In 



Maxillary gland. 

 Trachea. ' 



Lungs. * 

 Heart. 



Liver. 

 Gall bag. 



Colon. 



Caecum. 



Small intestine. 



Parotid gland. 



Pharynx. 

 Esophagous 



Thorax. 

 Aorta. 



Diaphragm. 



Stomach. 



Pancreas. 



Spleen, 



Kidneys. 



Colon. 



Abdomen. 



Rectum. 

 Bladder. 



Fig. 180. The Digestive Organs of a Monkey. 



animals living upon a mixed diet of animal and vegetable food, 

 the proportionate length of the intestine occupies an inter- 

 mediate position ; in many rodents and monkeys the propor- 

 tion is about 5 to 1 ; in man about 6 to 1 . It may be stated, 

 as a general rule, that the stomach is simple when the food 

 consists of easily-digested animal substances, and is more 

 complicated when the harder vegetable substances form the 

 sustenance of the animal ; wherever a plurality of stomachs 

 exist, there is one which is the true digestive cavity, the others 

 subserving the processes of maceration and preparation. 



[ 329. Upon minute examination with the microscope, the 

 mucous membrane of the stomach is found to be covered with 

 small glandular follicles, which open internally ; these aper- 

 tures are surrounded by an abundant vascular network, which 

 also extends more deeply, and includes the csecal and some- 

 what racemiform follicles. The glands are sometimes simple and 



