ELEPHANT AND MASTODON. 



69 



§ 2. On the Strtjctuee and Foem of the Molar Teeth. 



Plates I., II., and III. (F.A.S.)' are intended to represent, by 

 careful copies of nature, the modifications in structure and form 

 exhibited by the molar teeth of the Proboscidea ; they show, 

 in vertical sections, a series of gradations, commencing with 

 Dinothei'ium and Mastodon Ohioticus at one extremity, and 

 running through the other species to Elephas primigenius, in 

 which the greatest deviation ft-om the ordinary form of a 

 grinding tooth is met with. 



Each molar in the Proboscidea,^ as is the case with all other 

 animals, is developed within a closed membranous sac, called 

 the capsule, which is lodged in a cavity of the maxillary bone, 

 and which forms the mould, so to speak, of the tooth. The 

 exterior of this sac is simple, while its internal surface is 

 expanded into numerous folds which determine the arrange- 

 ment of the ' ivory,' ' enamel,' and ' cement,' entering into 

 the composition of the tooth. Prom the bottom of the sac a 

 gelatinous mass, the ' pulp nucleus,' is projected upwards, 

 subdivided into transverse digitated plates or segments, vary- 

 ing in number, length, and thickness in different species, and 

 more or less numerous in different molars of the same indivi- 

 dual, according to the age of the tooth. These ' j)ulp ' 

 segments are attached only by their base, and attenuate 

 gradually upwards to their summits, being entirely free from 

 adhesion, either to the opposite side of the sac or to the 

 contiguous 'pulp' divisions. The ossification of this 'pulp 

 nucleus,' by the deposition of calcareous matter within the 

 cells of its tissue, constitutes the ivory core, or central part of 

 the tooth, being the substance called ' dentine ' by Professor 

 Owen. 



From the opposite or coronal side of the capsule, other 

 folds or induphcations are given off, which proceed into the 

 spaces between the divisions of the ' pulp nucleus.' Their 

 attachment is continued along the parietes of the sac, so that 

 on every side, except the base, they envelope the jirocesses of 

 the ' puip nucleus,' over which they are closely applied, inter- 

 locking with the latter ; the two sets of processes thus form- 

 ing productions from the interior of the sac which are opposed 

 to each other in the manner of salient and re-entering angles. 

 The ossification of these peripheral folds in a continuous sur- 



' Here and in the remaining portion 

 of this memoir, the letters F.A.S. imply 

 that the plates referred to are to be 

 found in the ' Fauna Antiqua Sivalensis.' 

 "When these letters are not appended, 

 the plates are those of the present edition 

 of Dr. Falconer's works. — [Ed.] 



2 The substance of the four following 

 paragraphs is cbawn from the admirable 

 descriptions given by Cuvier in the 

 Ossemens Fossiles, torn. i. p. 32, and 

 by Owen in his valuable systematic work 

 on the teeth, Odontography, p. 649. 



