230 THE MEANING OF EVOLUTION 
actly the reverse plan. Using his tremendous head as 
a battering ram in fighting, and using his enormous 
tusks both in battle and in uprooting young trees, a 
lengthened neck is absolutely out of the question. 
Furthermore his front teeth have grown so prodi- 
giously that they would interfere with his getting his 
mouth to water. Accordingly, his nose has length- 
ened its tip until it reaches the level of his feet, and 
this nose becomes to him the main organ of grasp 
and of touch. To drink, its end is inserted in the pool 
and water is drawn up the nostril. If the animal were 
to attempt to draw it all the way back into his throat, 
it would inevitably strangle him by getting into his 
windpipe. Accordingly, when the nose is well filled 
with water, the tip of it is inserted in his mouth, and 
the water discharged by a quick puff. The horse has 
taken a method intermediate between these. It had 
moderately lengthened both neck and head in order 
to get to the ground with its nipping teeth, and thus 
to gather the grasses which serve as its principal food. 
The mammalian teeth, while of four kinds, really 
in most animals serve but two purposes. The front 
teeth consist of the incisors and canines, and are used 
for biting. The hind teeth, consisting of premolars 
and molars, are used for grinding. In the horse, the 
jaw has lengthened between these two sets, carrying 
the biting teeth far forward of the molars. It is this 
