MONKEY. 



267 



toward the sides, and not downward as in these. 

 There are six grinders in each side of the jaw, both 

 above and below, which is one more than is possessed 

 by any of the handed animals of the east, and conse- 

 quently they possess four more, or thirty-six in all, 

 while the others have thirty-two, as in man. None 

 of them are furnished with cheek-pouches or with 

 callosities on the buttocks, and all of them have the 

 tails long, very muscular, and prehensile. This last 

 character is the one which more immediately and 

 remarkably distinguishes them from the ground 

 apes, which they resemble in most other respects. 

 In this their distinguishing characteristic there are 

 two sub-divisions or sub-groups of them : one with a 

 tail naked of hairs, and only callous, or partially 

 scaly ; and the other having a tail covered with hair 

 to its extremity. On this account the first have been 

 called Gymnuri, or naked tails ; and the second Cebus, 

 which implies that organ is hairy. 



The Gymnuri have far more power in the tail than 

 the other ; and, if we except the kanguroo and the 

 whale, there are no animals in whose economy this 

 instrument is so serviceable. It is true that some 

 lizards, or at all events saurian reptiles, have prehen- 

 sile tails; and so have some mammalia which are not 

 handed, as, for instance, the little harvest mouse ; the 

 beaver, too, makes use of its tail as a rudder, and 

 even sculls with it in swimming, and also converts it 

 into a kind of third hind leg when building ; but the 

 uses of all these are far inferior to that of the naked 

 tail in these American monkeys. It is often very 

 long, considerably longer than the body ; and from 

 the number of its joints it can command space on 

 every side, and lay hold backwards or forwards, 

 upwards or downwards, to the one side or to the other, 

 with the same precision as if it were a hand, and 

 guided by the sight of an eye. From the direction 

 of the eyes in these animals it is not possible that the 

 prehensile tail can be guided by sight unless in very 

 particular instances ; and therefore they have naturally 

 in it the same exquisite sensibility of touch which 

 blind individuals of the human race acquire by long 

 experience and practice. The firmness of the grasp 

 which the animal can take by means of this tail is 

 much greater than one would readily believe, for if 

 it makes a single coil round a branch it is quite suf- 

 ficient not only to support the mere weight of the 

 animal, but to enable it to swing 1 in such a manner as 

 to gain a fresh hold with the hand. Not only this, for, 

 if the hands miss, the tail is sure to take hold, and 

 therefore, let the wind blow as it may, these animals 

 are never shaken from the trees. The power of mo- 

 tion is in the tail itself, and in every part of it, and 

 the muscular structure in which it resides is truly 

 wonderful. While the animal, in so far as the body 

 is concerned, is in a state of perfect repose, the tail 

 can, with the rapidity of lightning, feel about till it 

 gets a hold, and also try the stability of that hold ; 

 and if sufficiently stable, the animal, from the length 

 and elasticity of its legs, can throw itself upward, or 

 indeed in any direction, the coil of the tail being the 

 only fulcrum required. Some of the eastern monkeys 

 are very expert in their motions among trees ; but 

 there is no known species of mammalia nearly so well 

 adapted for being a tree animal as these naked-tailed 

 monkeys of America ; and we may add that no 

 forests are so well adapted for being the haunts of 

 expert tree animals as those which these singular 

 creatures inhabit. 



Those American monkeys with naked tails are 

 usually divided into four distinct genera. One of those 

 we have already described in the article ATELES, and 

 therefore our present notice may be restricted to the 

 three that remain, which we shall notice as briefly as 

 possible. 



HOWLING MONKEYS (Myctes). These animals, 

 which have also been called Steiitor, from the great 

 loudness of their voices, form a very natural and well- 

 defined genus. Their limbs are of mean length, with 

 five divisions on them all, and the thumb on the fore 

 ones about half the length of the second finger. One 

 of the most remarkable parts of their organisation is 

 the structure of the os hyoides, or bone of the tongue, 

 and of the instruments of sound with which the 

 remarkable enlargement of this part is connected. 

 This may be regarded as a sort of enlargement of the 

 larynx, which appears externally like a great swelling 

 or goitre, especially when the animal howls. So large 

 is this, indeed, that it gives a singular appearance to 

 the profile, by throwing the muzzle higher up than 

 what appears to be the centre of the face, an aspect 

 presented by no other race of animals. This singular 

 apparatus is so clearly and so popularly described by 

 Humboldt, in his Zoological Observations on the 

 Animals of Central America, that we cannot resist 

 quoting it. " The bony cone of the os hyoides," says 

 Humboldt, " measured by water, gave a size equal to 

 four cubic inches : the larynx was slightly attached by 

 muscular fibres, and communicated by a membranous 

 canal. The larynx consisted of six pouches, of ten 

 lines in length, to from three to five in depth. These 

 pouches resemble those of the small whistling mon- 

 keys, squirrels, and some birds. They have an open- 

 ing above on the same side with that of the glottis, by 

 which the air cannot enter without shutting the epi- 

 glottis. Above the pouches there are two others, of 

 which the lips or borders are yellowish. These are 

 the pyramidal sacs which enter into the bony case, 

 and are formed by membranous partitions. The air 

 is driven into these sacs, which are from three to four 

 inches long, and terminate in a point, but come in 

 contact with no part of the large hyoid bone opening 

 below. The fifth pouch is found in the opening of 

 the arythenoid cartilage, and is situated between the 

 pyramidal sacs of the same form, but shorter ; and 

 the sixth pouch is formed by the bony drum itself, 

 within which the voice acquires the mournful plain- 

 tive tone which characterises these animals." Alto- 

 gether the organisation of the neck and under jaw of 

 this animal is very peculiar, and offers some instances 

 of singular provision for a vast power of voice without 

 the least chance of injuring the essential parts of the 

 animal. In reality, the muzzle of the howling mon- 

 keys is rather elongated, and the facial angle small, 

 though the vast production of the howling apparatus 

 renders this not perceptible. The occipital hole, 

 through which the spinal cord passes from the skull 

 to the vertebrae, is situated as far upwards as the 

 orbits of the eyes, and directed backwards, not down- 

 wards, by which means the spinal cord is secured from 

 all injury which could arise from the pressure of vio- 

 lent action carried on in front. The lower jaw is 

 very much developed both in its body and its branches, 

 so that their depth is nearly equal to the entire height 

 of the cranium. Between these extended walls the 

 principal modifications of the os hyoides are placed. 

 The body of that bone is formed into an osseous case 

 or shell, the walls of which are very thin and elastic. 



