470 The Outline of Science 



Food-getting among Mammals 



The Great Ant-eater (Myrmecophaga) of South America 

 comes out at night and with its exceedingly powerful claws breaks 

 into the earthen hills of the termites. Then out and in whips the 

 thread-like sticky tongue, drawing hundreds of insects in a short 

 time into the absolutely toothless mouth. The same kind of 

 tongue is seen in other ant-eaters, such as the Aard-vark of 

 South Africa, and in the oviparous Echidna, which is also 

 absolutely toothless. 



The whalebone whale, of whatever kind, swims open- 

 mouthed through the surface waters, engulfing myriads of small 

 sea-snails and the like in the huge gaping cavern. The small 

 animals are caught on the frayed edges of the baleen plates, 

 exaggerated horny ridges of the palate, which hang downwards 

 from the roof of the mouth. Every now and then the whale 

 raises its tongue and brushes a multitude of the entangled 

 creatures towards the back of its mouth, where they are gripped 

 by the pharynx and swallowed. The water streams out at the 

 sides of the mouth through the sieve of whalebone, but some of it 

 would be apt to "go the wrong way" were it not that the whale 

 shunts its glottis (the opening to the windpipe) forward to 

 embrace the posterior end of the nasal passage. What a contrast 

 is such a mouth to that of a toothed whale, like the Sperm-Whale 

 and the Dolphin, with teeth well suited for seizing cuttlefishes 

 and fishes! Yet it is interesting to notice that the whalebone 

 whale has before birth two sets of teeth, which never cut the 

 gum! 



The adaptations of the teeth of mammals to different kinds 

 of food-getting are many ; but from a few we may learn all. In 

 the gnawing mammals or rodents, such as rats, beavers, porcu< 

 pines, and squirrels, the enamel is either confined to the front of 

 the incisors, or it is much more strongly developed in front than 

 it is behind. Thus the posterior part of the tooth wears away 

 faster than the anterior part, so that a chisel edge is automatically 



