376 ANATOMY OF VERTEBRATES. 



We are thus enabled, with the same scientific certainty as that 

 whereby we recognise in the middle toe of our foot the homologue 

 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, fig. 293, I., as the homologues of the great carnassial teeth 

 of the Lion, p 4, m l, ib. v. 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 l 

 and p 2 in the Bear, ib. II. 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. 



The homologous teeth being thus determinable, they may be 

 severally signified by a symbol as well as by a name. The 

 incisors, e.g., are represented in the present work by their initial 

 letter i, and individually by an added number, i l, i 2, and i 3, 

 counting from the medial line outwards ; the canines by the 

 letter c; the premolars by the letter p; and the molars by the 

 letter m ; these also being differentiated by added numerals. 

 Thus, the number of these teeth, on each side of both jaws, in 

 any given species, Man, e.g., may be expressed by the following 

 brief formula : — 



.2.2 1.1 2.2 3.3 _ , 

 1 ^— , ; c --- ; » - — ; m — - = 32 - 

 2.2' 1.1'^2.2' 3.3 



and the homologies of the individual teeth, in relation to the 

 typical formula, may be signified by i l, i 2; c; p 3, p 4; m l, m 2, 

 m 3 ; the suppressed teeth being i 3, p i , and p 2. 



The soundness of the foregoing conclusions as to the nature of 

 the teeth absent in the reduced dental formula of Man, is exem- 

 plified by 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 Quadrumanous series, the 

 same number and kinds of teeth are present as in Man, the first 

 deviation being the sexual 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 Gorillas, Chimpanzees and Orangs, together with 

 the sexual difference in the proportions of the canine teeth. Then 

 comes the added premolar in the New World Monkeys, fig. 251, 



