32 



these animals possesses supercilliary ridges, which are wanting in 

 the ourang. 



The head of the ourang, viewed in front, is pear-shaped, expand- 

 ing from the chin upwards, the cranium being much the larger 

 end. The frontal sinuses are very large in the dog, wolf, porcu- 

 pine, sloth, sheep, bull, pig, horse, and especially in the elephant; 

 they are small in bats, rats, squirrels, ant-eaters, the hippopotamus, 

 rhinoceros, &c. In cats, martens, and bears, the parietal bones 

 give off from their inner and posterior edge a process of bone 

 which projects into the cavity of the skull, and forms a perfect 

 bony tentorium cerebelli. In the dog and horse, similar processes 

 arise from the petrous portion of the temporal bones. 



The lower jaw is subject to many varieties in the mammalia. 

 In the whale it resembles two enormous ribs, united at the point, 

 without any trace of ascending rami or coronoid processes. The 

 articular head here, as well as in the porpoise, is directed back- 

 wards, and is attached to the skull by means of strong cellular 

 tissue, filled with oil. 



In the hare, rabbit, and guinea-pig, of the order rodentia, the 

 coronoid process is very small; in others, as squirrels and rats, it 

 is pretty large. The condyloid, or articular process, is compressed 

 latterally, directed from behind forwards, and larger in front than 

 behind. 



In the carnivora, the articular head is directed transversely, and 

 so closely adapted to the glenoid cavity of the temporal bone that 

 the jaw retains its situation after the destruction of the ligaments. 

 This is well seen in the marten and sea-otter. In the ruminants 

 the condyle is very flat, to admit of the lateral motion necessary 

 during the process of rumination. In the carnivora, rodentia, and 

 ruminantia, the two halves of the lower jaw are never firmly 

 united — in this particular affording us an instance of the perma- 

 nence of a condition in other mammalia, which in man is peculiar 

 to the earliest periods of life. 



Swine have two small bones placed at the aterior openings of 

 the nares for the support of the snout. In fine, it is to be remarked 

 that the crania of all the quadrumana, together with the other 

 mammalia, are distinguished by the comparative size, great'length 

 and projection of the jaws. 



Anterior extremity. — This extremity in the lower animals cor- 

 responds to the superior of the human subject, and contains all 

 the elements of it. modified according to the habits of the animal. 

 Sometimes connected to the trunk by means of muscle only, as in 

 the cetacea, pachydermata, ruminantia, and solipe a; in other in- 

 stances by ligament and muscle, as seen in the insectivora. 



Clavicle. — The importance of this bone, in the motions of the 

 upper or anterior extremity, may be well estimated by the fact of 

 its being present in those animals only whose habits of life require 

 free and varied motions of the shoulder. Thus in the quadrumana 

 it is strong and curved, as in the human subject. The bat, hedge- 



