OF DOMESTICATED ANIMALS. 
475 
union of the carnivorous and the omnivorous tooth ; it marks out 
the future destiny of the first genus of the second subdivision of 
the digitigrades. 
The second true molar in the upper jaw is also a compound 
tooth, and characteristic of the habits of the animal; partly a 
carnivorous tooth, to seize the prey for his master’s use, and part¬ 
ly an omnivorous one, that he may be able to assimilate himself 
to the food of the master he is to serve. It extends itself across, 
and not like the others along, the jaw, occupying no little portion 
of the palatine arch; it presents, outwardly, two prominent 
sharp and cutting points, while the inner half is perfectly tuber¬ 
culous. The bicuspid points lap over the outer edge of the se¬ 
cond molar in the lower jaw, and cut and tear the food; the 
tuberculous part corresponds and fits with the whole tuberculous 
surface of the lower tooth, and so crushes that which has been 
already torn. The wearing of this tooth—the breaking off or 
rounding of the acuminated points—the rounding of them and 
of the trenchant edges—the flattening of the tuberculous surface 
are evident enough; but the progress and rapidity of these 
changes will depend as much on the kind of food as on the age 
of the dog, and will be more rapid in the large and powerful dog 
than in the smaller one, on account of the additional strength of 
muscle employed on the teeth. 
The last true molar tooth is a perfect tubercular one, still more 
confirming the mingled character and habits of the animal; it 
also lies across the jaw. It meets the last molar in the lower 
jaw, and helps with it to crush the food. The three superior 
true molars united together present another change correspond¬ 
ing with the age of the dog. The operations of bruising and 
crushing the food depend almost entirely on them, the whole la¬ 
bour and stress is thrown upon them. They lie—the first in a 
little degree; and the two last entirely across, and not along the 
jaw; the force is made to act upon a shorter and smaller base. 
The altered form of the upper jaw gradually shews the accumu¬ 
lated power acting here : it yields—it bows out—it becomes, 
and by degrees the outer wall of the jaw assumes the same 
form—it becomes a true segment of a circle. The comparison 
between the form of this portion of the outer surface of the upper 
jaw in a young and an old dog is very singular. 
The second posterior molar of the lower jaw is a tubercular 
tooth, lying along the jaw, and corresponding partly with the 
second, and partly with the last molar of the upper. Its indica¬ 
tions of age are confined to the increasing smoothness of its 
surface. 
The last posterior molar of the lower jar is very small. It is 
