15A 



KNOWLEDGE 



[Jii.Y li, 169-1. 



own, Lavirg the angles of their crowns rounded oflf, and 

 carrying on their grinding-surfaces four very blunt 

 tubercles, placed alternately to one another, as well as a 

 somewhat Eiaaller tubercle at the hinder end. On the 

 other hand, in the monkeys the molar teeth are obkng in 

 form, and carry four very prominent tubercles arranged in 

 pairs at the two extremities of each, and each pair being 

 connected so as to foim a couple of more or less well- 

 defined transverse ridges extending right acioss the 

 crown. Then, again, whereas in tie man-like apes the 

 last molar, or " wisdom-tooth," in the lower jaw is similar 

 in form to the two teeth in front of it, in the great majority 

 of the Old World monkeys this tooth has a large projecting 

 heel at its hinder end. These dental chaiacters afl'oid 

 very important evidence of the close kinship of the man-like 

 apes to man himself, and undoubtedly outweigh the 

 difference in the foim of the whole dental seiies now to be 

 noticed, which is largely due to adaptaticn. In both the 

 upper and lower jaws of man, the teeth, as we all know, 

 are arranged in a regular horseshoe series, with scarcely 

 any interruption to the continuity by the tusks, which are 

 but little taller than the other members of the series. 

 In the adults (and especially the males of the larger 

 species) of the man-like apes the cheek-teeth are arranged 

 in a nearly straight line, and form a more or less 

 angulated junction with the line of the incisors ; the 



Side Tiew of the head of " Jennv,' 



tlie Chimpanzee, in the Zoologieal Q-ardeiis. 

 Mr. BiUivard. 



the two 

 in con- 

 resemble 

 a young 



large tusks occupying the angle between 

 series, and thus forming a marked break 

 tinuity. In these respects the man -like apes 



their inferior kindred. If, however, we take _, _, ^ 



individual of the larger anthropoids, and especially the 

 chimpanzee, it will be found (as shown in our illus- 

 tration) that the teeth, owing partly to the imperfect 

 protrusion of the tusks, form a much less interrupted and 

 more regularly curved series. Indeed, with the exception 



that the whole jaw is longer and narrower, and the 

 partially protruded tusks are proportionately larger, the 

 characters of the figured specimen make a very marked 

 approximation to the human type ; and the jaw of a 

 chimpanzee at this stage may be regarded as almost 

 intermediate in structure between that of man and that 

 of an adult male gorilla. Moreover, in this juvenile state 

 the bony union of the two branches of the lower jaw 

 partakes of the short and rounded form characterizing 

 that of man ; whereas in the adult it becomes longer and 

 more deeply channelled, like that of the lower monkeys. 

 In many respects the teeth and jaws of the gibbons, or 

 smallest representatives of the group under consideration, 

 conform to the inteimediate type. Not cnly aie the 

 human characteristics most developed in the teeth and 

 jaws of the young of the larger man-like apes and the 

 gibbous at all ages, but the ssme is tiue with regard 

 to (he skull of the foimer. The skull of the young 

 gorilla, for instance, lacks the beetling crests over the 

 eyes and the prominent ridge down the middle of the 

 crown which give such a forbidding and repulsive aspect 

 to the cranium of the full-grown male. This loss 

 of human resemblances is due to specialization taking 

 two difl'erent lines in man on the one hand, and in 

 the larger man-like apes en the other; the development 

 in the one case tending to^increased size of brain, coupled 



with no mai'ked in- 

 crease in the size of 

 the tusks, while in the 

 other the brain grows 

 at a less rapid rate, 

 and the skull and tusks 

 (more especially in the 

 male)assume characters 

 approximating them to 

 those of the inferior 

 animals. Both in men 

 and apes the young con- 

 dition may accordingly 

 be regarded as the most 

 generalized. 



Among the other 

 features in which the 

 man - like apes ditter 

 from monkeys and re- 

 semble man, are the 

 absence of dilatable 

 pouches in the cheeks 

 for the storage of food, 

 and the total loss of the 

 tail, as well as the flat- 

 tened, instead of later- 

 ally compressed, form 

 of the breast-bone ; the 

 gibbons alone retain- 

 ing the naked patches 

 on the buttocks so 

 characteristic of the 

 monkeys, but only 

 in a much reduced 

 gorilla and chimpanzees further differ 

 of the group, and thereby re- 

 the so-called central bone 

 a nearly central position 



From a photograph b}' 



condition. The 



from the other members 



semble man alone, in the loss of 



of the wrist — a bone occupying 



between the upper and lower rows of small bones of which 



that joint is composed. What may be the object of the 



disappearance of this bone, it is not easy to say ; but the 



fact that it is wanting in the two genera of apes just 



mentioned is very significant of their close structural 



