176 



HIGH SCHOOL ZOOLOGY. 



are able to secure and to bolt, without previous mastication, in 

 a very short time, a large amount of food, which they after- 

 wards masticate when they have got to some secure I'etreat 

 The mechanism concerned may be studied in the sheep's 

 stomach, where the cardiac end has two compartments, the larger 

 Rumen {paunch), and the smaller Reticulum {lion<njcomli)y while 

 the pyloric end has similarly two compartments, the Psalterium 

 {manyplies), and the Abomasum {rennet stomach). The 

 oesophagus is attached between the rumen and the reticulum, 

 and the grass which is hastily swallowed passes first into these 

 compartments ; it is then moved from one to the other, and 

 finally thrown back into the mouth and subjected to a thorough 

 mastication and insalivation, after which the semi-fluid product 

 is again swallowed and strained off into the abomasum and in- 

 testine, through the psalterium, which is connected- indirectly 

 with the ossophagus by a half-groove on the wall of the 

 iieticulum, capable of being converted into a complete channel. 



A peculiar dentition accompanies the ruminant stomach ; in 

 the typical forms it is i§, c^, m§, there being only a pad in the 

 upper jaw, against which the lower incisors and incisor-like 

 canines bite. A wide gap separates the front teeth from the 

 molars, which have flat crowns with semilunar folds of enamel 

 on the surface. Such teeth are therefore said to belonsr to 

 selenodont forms, in contradistinction 

 to the tuberculate teeth of hunodont 

 forms, but it is obvious (as in the 

 Hippopotamus, e.g.,) that a tuberculate 



tooth when worn down may present a Fi<,Mi6.-Molarsfrom the up- 

 peculiar pattern of enamel, and there- rnrTossnArtitvitS" 

 fore bunodont forms are regarded ^s "'^"''''^ '^"^ '^''^^'''"^''"• 

 more primitive (Fig. 116). 



The feet are also different in their structure in the ruminant 

 forms, for not only are the second and fifth toes raised off" the 

 ground, becoming dew-claws, but they often disappear, and 



