42 THE OSTEOLOGY AND MYOLOGY 



hold of the loosely hanging hind feet ; further action of all four extremities carries the 

 paws to the root of the tail, which is firmly grasped, when the animal climbs up its tail 

 "hand over hand " until the point of support is laid hold of; after Avliich, by a peculiar 

 squirming motion of tlie whole body, the desired attitude is attained. The same power of 

 flexion is brought largely into play in most scansorial movements. Lateral motion of the 

 body is also unusually free. The neck is short and thick ; its motion is chiefly that of flex- 

 ion. The head is of moderate size, appearing in life scarcely separated from the body, reg- 

 ularly cone-shaped, with little, if any, constriction at base, tapering gradually to a slender, 

 elongated muzzle. The nostrils open at the sides of the extremity of the truncated, hog- 

 like snout ; the animal is reputed to have excelleni olfactory powers, and the supposition 

 is borne out by the large nasal chambers and sense capsules. The eyes, placed far up on 

 the sides of the head, are small, with rather poorly developed lids ; presumably in rela- 

 tion to eminently nocturnal habits. The external ears are extremely large, rounded, thin 

 and membraneous, mostly naked, suggesting those of certain cheiroptera ; the sense of 

 hearing must be judged acute, if characters of the pinna afTord a criterion. The rictus 

 is long and ample ; the lips thin and scanty ; the large and numerous teeth are a con- 

 spicuous feature ; the upper canines protrude beyond the lip, and lie outside the lower 

 lip when the mouth is closed. 



The opossum is pedimanous ; as truly four-handed, perhaps, as many, or any of the 

 quadrumana. The well-developed clavicles of the fore-limb, and the free coxo-femoral 

 articulation of the hind one, permit both extremities to be Avidely separated, each from 

 its fellow, and render easy the " hugging " movements necessary in climbing. Pronation 

 and supination of the forearm are perfect ; the wrist joint, besides revolving freely upon 

 the ulna, is capable of great extension and flexion ; of abduction and adduction in less 

 degree. The fingers have much the same relative lengths as those of the human hand ; 

 but there is less difference between them, the little finger especially being comparatively 

 longer and stouter, and the thumb longer, less divaricating from the axis of the other 

 digits, and less freely opposable. This condition of the thumb results mainly from the 

 more nearly perfect parallelism and closer union of its metacarpal bone ; still it is " oppos- 

 able," in the proper sense, and may easily be brought in contact with the tip of any finger, 

 or of all together. The five anterior digits are unguiculate ; the claws are non-retractile, 

 and therefore stout, short, blunt and only moderately curved. The member, as a whole, 

 is to be reckoned among the more perfect hands afforded by animals lower than man. 

 Its ambulatorial function is secondary in importance ; it finds its highest and proper use 

 in climbing, in gathering food, and conveying it to the mouth ; and in conjugal and 

 maternal offices. The foot is nearly as much of a " hand " as the hand itself; it is 

 equally fitted for grasping. The hallux, compared with the thumb, is even shorter, 

 and more inclined from the axis of the other digits, to which it is freely opposable. It 

 bears no claw ; it is club-shaped, with a rounded extremity ; in place of the claw there is 

 a well-marked semilunar groove. The other toes are unguiculate ; the claws are like 

 those of the fingers, but longer, slenderer and more curved ; the first three toes are of 

 nearly equal lengths, and united by continuous integument beyond the first joints ; the 

 little toe is much shorter, but relatively, if not absolutely, stouter than the rest. The 

 general shape of the foot recalls the quadrumanous type. The movements at the ankle 

 are remarkably free, and seem to be more than simply analogous to those of the wrist. As 



