MAMMALIA. 



377 



There arc eiglit on each side of the upper, and also of the 

 lower jaw; thus amounting in all to thirty -two.* 



A few species of mammalia, as the Ant-eaters, are entirely 

 devoid of teeth ; in others there is a great diversity as to their 

 number. The female Narwhal has two teeth, and both are 

 concealed in the substance of the jaw. The Australian Water- 

 rats have twelve. Most gnawing animals have twenty ; but 

 the Hares and Rabbits have twenty-eight. The Porpoise has 

 between eighty and ninety, and the true Dolphins from one 

 hundred to one hundred and ninety .f 



It is found that the arrangement of the teeth varies, accord- 

 ing as the food is to consist of animal or vegetable substances, 

 of soft flesh or horny covered insects ; of tender herbs, or wood 

 of greater or less degree of hardness. Hence it is possible, 

 merely by an inspection of the teeth, to determine, with con- 

 siderable certainty, the diet, the habits, and even the general 

 structure of most of the mammalia.;]: 



We never meet in nature with an incongruous union of 

 parts. A Lion with the hoof of a Horse, could not subsist ; 



Fig. 298.— Skcll or a GxAWina Asimai. 



Fig. 299.— Skull of a Boar. 



it would die of hunger from inability to seize and retain its 

 prey. In like manner, a Horse, with the teeth of a Lion, 

 would starve in the midst of the finest pastures, from being 

 unable to crop and triturate its food. 



• Zoolo^ts have adopted a formuKi for expressing the number of teeth 

 possessed by different animals at each side of the mouth, distinguishing those 

 in the ui)per jaw from those in the lower jaw. - The dental formula of man 

 is written thus: — 



2—2 1 — 1 2—2 .3—3 



Incisors ; Canines ; Premolars ; Molars ; ^ 32. 



2—2 1—1 2—2 3—3 



t Owen's Odontography, 

 i M. Edwards' Ele'mens. 



