514 CARNIVORES. 



the most part associated together and with the pulp-cavity by 

 medullary canals. The calcigerous tubes radiate from those central 

 cavities, in all directions, with sub-parallel, diverging curvatures ; 

 dividing, subdividing and sending off numerous branches, which 

 anastomose with those of the adjoining masses, and, where these 

 are situated next the dentine, with the tubes of that tissue. In 

 each lobe of the osteo-dentine the concentric rings parallel with 

 the contour of the central medullary cavity, are well-marked. 

 Myriads of minute calcigerous cells are dispersed throughout the 

 osteo-dentine. 



The pulp-cavity of the incisor and molar teeth of the Walrus 

 is filled up by a smaller quantity of the osteo-dentine. Minute 

 vascular canals convey the capillary blood vessels to this structure 

 from the vascular membrane attached to the solid base of the molars, 

 and, in the tusks, from the persistent pulp which fills the basal cavity. 



190. Classification and analogies of the molar teeth of the Carnivora. 

 — ^The various forms of the teeth composing the molar series and their 

 concomitant diversity of function in the order Carnivora have led to 

 their being divided into distinct groups, to which the Anatomists, 

 who have more especially devoted themselves to the study of those 

 organs, have generally assigned special names. The most com- 

 monly adopted classification and nomenclature of the molar teeth, 

 especially, as they exist in the Carnivora, is that proposed by 

 Mr. F. Cuvier in his celebrated work the ' Dents des Mammiferes ;' 

 where, treating of the ' macheli^res,' cheek-teeth, or molar teeth, 

 he says : " Ces derni^res se partagent en trois divisions. La 

 premiere se compose de deux a quatre dents qui viennent apr^s 

 les canines, dont I'usage est assez indetermine, et qui sont ' des 

 fausses molaires.' La seconde ne se compose jamais que d'une 

 dent qui est la carnassiere ; c'est en elle que reside essentiellement 

 la faculte de couper les fibres de la chair. La troisieme est celle 

 des dents tuherculeuses, dont le nombre ne s'el^ve jamais au-dela 

 de deux et qui paraissent avoir pour destination principale de 

 bfoyer les alimens susceptibles de I'^tre." p. 77. The dentition 

 of the different genera is numerically formulised, according to the 

 foregoing classification : thus the genus Felis has : machelieres I ; 

 dont-4 fausses molaires, +-|-carnassi^res, + i- tuherculeuses. 



