MAMMALS 



213 



riedly and to retire to a safe place to chew it. Rudiments of 

 the upper incisors are present in the jaw of the calf, show- 

 ing the descent from animals which had a complete set of 

 teeth. The rudiments are absorbed and the upper jaw of 

 the cow lacks incisors entirely, as they would be useless 

 because of the cow's habit of seizing the grass with her 

 rough tongue 

 and cutting it 

 with the lower 

 incisors as the 

 head is jerked 

 forward. This 

 is a more rapid 

 way of eating 

 than by biting. 



Which leaves ?!£ 386. ^ SKELETON OF COW Compare with horse 



(Fig. 395) as to legs, toes, tail, mane, dewlap, ears, body. 



the grass shorter 



after grazing, a cow or a horse ? Why ? Grass is very 

 slow of digestion, and the ungulates have an alimentary 

 canal twenty to thirty times the length of the body. 

 Thorough chewing is necessary for such coarse food, and 

 the ungulates which chew the cud (ruminants) are able, 

 by leisurely and thorough chewing, to make the best use 

 of the woody fibre (cellulose) which is the chief substance 

 in their food. 



Ruminants have four divisions to the stomach. Their 

 food is first swallowed into the roomy paunch in which, 

 as in the crop of a bird, the bulky food is temporarily 

 stored. It is not digested at all in the paunch, but after 

 being moistened, portions of it pass successively into the 

 honeycomb, which forms it into balls to be belched up and 

 ground by the large molars as the animal lies with eyes 

 half closed under the shade of a tree. It is then swai- 



