138 ELKMI:NTS OF MAMMALIAN ANATOMY. 



mastication, and then passes direct, by means of a 

 groove in the esophagus, into the psalterium, and finally 

 on to the abomasum. The latter is the true stomach, 

 and is provided with gastric glands. In the camels the 

 rumen and reticulum have connected with them pouch- 

 like diverticula for the storage of water. The con- 

 stricted openings of the pouches into the rumen or 

 reticulum may be entirely closed by sphincter muscles. 



In man and the higher apes there is present an at- 

 tenuated extension of the cecutn known as the vermi- 

 form appendix. In the fetus of man it is proportionally 

 longer than in the adult. In the herbivorous mammals, 

 such as the cow and rabbit, the cecum is greatly enlarged, 

 so as to play an important part in digestion. In a few 

 forms, such as the sloths, some Cetacea, and a few 

 Carnivora, the cecum is absent. 



The lowest mammals, the Monotremata, resemble 

 birds and reptiles in possessing a cloaca into which open 

 the rectum and the urinary and genital ducts. The cloaca 

 opens externally beneath the tail. Salivary and thyroid 

 glands, pancreas, and liver are present in all mammals, 

 but the gall-cyst is absent in Cetacea, the Perissodactyla, 

 Hyracoidea, and a few Rodentia. The liver is usually 

 relatively larger in fat-eating animals. 



PRACTICAL QUESTIONS AND SUGGESTIONS. 



1 . Describe the fauces. 



2. Describe in detail every feature visible on the dorsal surface of 

 the tongue. 



3. Give the number "of fangs in each tooth of the permanent set. 



4. Give the number of each kind of teeth in the two sets. 



5. Draw two aspects of the sectorial tooth. 



6. How thick is the enamel of the teeth? 



7. Name some mammals which do not have enamel on the teeth. 



8. Name some toothless mammals. 



9. Name some mammals having only one set of teeth. 



