THE COW 239 
In the calf is a beautiful example of adaptation of 
structure to altered conditions. When the animal lives on 
milk, the first three stomachs are not necessary, as the 
food requires no preparation for digestion ; hence, at first, 
the reed, or fourth division, is larger than all the rest 
taken together. As soon, however, as the calf begins to 
feed on solid food, the process of rumination begins, and 
the other three parts develop rapidly, until the rumen or 
paunch is larger than all the rest. 
Notr.—All horn-bearing animals are ruminants. This does 
not mean that all ruminants are animals with horns, for the 
Camel and Musk-deer are without them ; but that the presence of 
horns indicates that the animal is a ruminant. 
The horns. The top of the head is usually furnished 
with a pair of curved horns, which are really outgrowths 
from the frontal bones, Each horn consists of a hard bony 
core, and an outer horny case. The core is an outgrowth 
from the bones of the skull, and the case an outgrowth 
from the skin. 
Fig. 140.—Horny Case. Fig. 141.—Bony Core. 
The horns are the weapons with which the animals 
defend themselves from their enemies and fight with their 
fellows. It will be noticed that the horns of the Cow are 
much larger and longer than those of the Bull, This is 
because, when wild, it was the Cow who was most 
frequently called on to defend her. offspring from the 
