TEETH. 



917 



initiation of the exact homologies of the teeth, 

 it is satisfactory to know that the more 

 constant and important character of develop- 

 ment gives the requisite certitude as to the 

 nature of the so-called bicuspids in the human 

 subject. In fig. 584... the condition of the 



Fig. 58-1. 



12 



Deciduous and permanent teeth of a Child (Homo). 



teeth is shown in the jaws of a child of about 

 six years of age. The two incisors on each 

 side (di.) are followed by a canine, dc., and this 

 by three teeth having crowns resembling 

 those of the three molar teeth of the adult. 

 In fact, the last of the three is the first of 

 the permanent molars ; it has pushed through 

 the gum, like the two molars which are in 

 advance of it, without displacing any previous 

 tooth, and the substance of the jaw contains 

 no germ of any tooth destined to displace it : 

 it is therefore, by this character of its de- 

 velopment, a true molar, and the germs of 

 the permanent teeth, which are exposed in 

 the substance of the jaw between the diverging 

 fangs of the molars, d. 3 and d. 4, prove those 

 molars to be temporary, destined to be replaced, 

 and prove also that the teeth about to displace 

 them are premolars. According, therefore, 

 to the rule previously laid down, we count 

 the permanent molar in place the first of its 

 series (m. 1), and the adjoining premolar as 

 the last of its series, and consequently the 

 fourth of the typical dentition, or p. 4. 



We are thus enabled, with the same scien- 

 tific certainty as that whereby we recognise 

 in the middle toe of the foot the homolonue 

 of that great digit which forms the whole 

 foot and is encased by the hoof in the horse, 

 to point to p. 4, or the second bicuspid 

 in the upper jaw, and to m. 1, or the first 

 molar in the lower jaw of man, as the homo- 

 logues of the great carnassial teeth of the lion 

 and tiger. We also conclude that the teeth 

 which are wanting in man to complete the 

 typical molar series, are the first and second 



premolars, the homologues of those marked 

 p. 1 and p. 2 in the bear. The characteristic 

 shortening of the maxillary bones required 

 this diminution of the number of their teeth, as 

 well as of their size, and of the canines more 

 especially ; and the still greater curtailment 

 of the premaxillary bone is attended with a 

 diminished number and an altered position of 

 the incisors. One sees, indeed, in the car- 

 nivorous series, that a corresponding decrease 

 in the number of the premolars is concomitant 

 with the shortening of the jaws. Already in 

 the Mustdida:, (fig. 580., IV), p. 1 below is 

 abrogated; in Feat also above, with the further 

 loss ofj). 2 in the lower jaw ; the true molars 

 being correspondingly reduced in these strictly 

 flesh-eating animals, but taken away from the 

 back part of their series. 



if we were desirous of further testing the 

 soundness of the foregoing conclusions as to 

 the nature of the teeth absent in the reduced 

 dental formula of man, we ought to trace the 

 mode in which the type is progressively 

 resumed in descending from man through the 

 order most nearly allied to our own. 



Through a considerable part of the Qua- 

 drumanous series, e. g. in all the Old World 

 genera above the Lemurs, the same number 

 and kinds of teeth are present as in man ; 

 the first deviation being the disproportionate 

 size of the canines and the concomitant break 

 or "diastema" in the dental series for the 

 reception of their crowns when the mouth 

 is shut. This is manifested in both the 

 Chimpanzees and Orangs, together with a 

 sexual difference ha the proportions of the 

 canine teeth. 



As the precise characteristics of the human 

 dentition are best demonstrated by comparison 

 with that brute species which is most nearly 

 allied to Man, and makes the first step in the 

 descending scale, I here subjoin the details of 

 such a comparison, which is the more required 

 since it is not touched upon in the article 

 QUADRUMANA, and will be the more acceptable 

 as one of its subjects is a species of Chim- 

 panzee ( Troglodytes Gorilla) *, unknown to 

 science when that article was written, and 

 which, so far as its organisation is known, is 

 more anthropoid than even the docile and 

 smaller species of Chimpanzee (Troglodytes 

 nigcr). A side view of the teeth of a male, 

 full-grown, but not aged, specimen of the 

 great Chimpanzee is given of the natural size 

 in jig. 585., and a view of the working surface 

 of the whole series of the upper jaw in Jig. 586. 

 This dentition, though in all its principal 

 characters strictly quadrumanous, yet, in the 



* Drs. Savage and "Wyman, Boston Journal of 

 Natural History, 1847 ; Owen, Transactions of the 

 Zoological Society, vol. iii. p. 381 (February, 1848). 

 M. F. Cuvier has not given a figure of the dentition 

 of any species of Chimpanzee (Troglodytes}. Be- 

 lieving with his brother, that the Orang (Pithecus, 

 GeoftV.) made the nearest approach to in;in, the 

 dentition of an immature Pithecus Wurmbii with 

 one of the characteristically large permanent molars 

 (m. 1) in place, immediately follows the plate of the 

 human dentition in the " Dents cles Maminiferes," 

 8vo. pis. i. & ii. 



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