Modifications of Teeth. 1 1 3 



position, arc lilted to cut and tear. Their points 

 are sharp, and those in the upper and lower jaws 

 pass each other like scissor-blades. In those that 

 feed upon insects, fine, sharp points fit into cor- 

 responding indentations. 



In herbivorous animals, the modifications are 

 numerous, but always adapted to the food. In the 

 horse, the layers of hard and soft material alternate 

 in the crown of the tooth, so that under constant 

 use the surface of the tooth is like a millstone that 

 is picked by the very process of g rinding. And in 

 the moose and deer that browse, the tooth grows 

 sharp upon the outer edge like a chisel. The 

 mouth of t' :;land whale is another marked 



case of adaptation in an animal for the food upon 

 which he lives. This largest animal upon the globe 

 Is upon the minute mollusks and crustaceans 

 that float in countless numbers in the northern 

 F<>r such food, teeth would be useless. His 

 huge mouth is titled with a strainer formed by the 

 fringes of the whalebone plates. By this curiously 

 constructed net he gathers his food from tbe 

 waters. 



In the mouths of some rays and other fishes that 

 feed upon shell- fish, there is a solid pavement of 

 bone, both above and below, for crushing the shells. 

 In birds where no teeth are found, and the food is 

 mostly solid seeds, a compensation is found in the 

 crop, in which the food is held for a time and gra- 

 dually dropped into the powerful muscular stomach 

 fitted to grind as well as digest. 



