VOL. LXXXIX.] PHILOSOPHICAL TRANSACTIONS. 51Q 



elephant's grinders are originally formed, my short stay at Tiperah did not allow me 

 sufficient opportunities to investigate; but, since my return to England, I have had 

 frequent conversations with my friend Mr. Home on that subject, who, from an 

 examination of the teeth brought home by me, and some preparations in the late 

 Mr. Hunter's collection, has been able to prosecute the subject with considerable 

 success. His observations will be laid before the e. s., immediately after the pre- 

 sent paper, as a continuation of the same subject. 



XIV. On the Structure of the Teeth of Graminivorous Quadrupeds; particularly 

 those of the Elephant and Sus JEthiopicus. By E. Home, Esq., F. R. S. p. 237. 



When Mr. Corse put into my hands his observations on the elephant's teeth, 

 and showed me the teeth themselves in their different stages of growth, in illustra- 

 tion of what he had advanced on the subject, I very readily engaged in the prosecu- 

 tion of so curious an investigation. I examined several specimens of elephants' 

 teeth, preserved in spirit, while in a growing state, which are deposited in Mr. 

 Hunter's collection of comparative anatomy, and compared them with the teeth in 

 Mr. Corse's possession. From these 2 sources, I was enabled to procure every in- 

 formation that was required, to explain the structure of the elephant's teeth, and 

 to point out the general principle on which all teeth are formed, that have the ena- 

 mel intermixed with the substance of the teeth ; a subject, as far as I am acquainted, 

 not hitherto investigated. To make my observations on the structure of the com- 

 plex tooth of the elephant intelligible to the r. s., it appears necessary to mention, 

 generally, the mode in which the more simple teeth of the human species, and of 

 carnivorous animals, are formed: this knowledge will render the account of such 

 additional parts as are met with in those of the elephant, more easily understood. 



The teeth of carnivorous animals are formed from a vascular pulp, of the same 

 shape with the future tooth, on the external surface of which the substance of the 

 tooth begins to grow, and increases till it is completely formed. The pulp is in- 

 closed by a capsule, the cavity of which, while the tooth is growing, is filled with 

 a viscid fluid, similar to the synovia of joints; and this fluid, by the absorption of 

 the thinner parts, becomes inspissated to a proper state for crystallization, so as to 

 form the enamel, which adheres to the surface of the tooth. Teeth formed in this 

 way, are composed of 2 parts, of dissimilar texture: one, the enamel, which is 

 striated; the other, the substance of the tooth, which is laminated, like ivory, 

 being more compact than common bone, and less so than the enamel; but differing 

 from both in the mode of its formation. Bones are formed in 2 different ways: 

 those that are cylindrical, have cartilage for their basis; those that are flat, either 

 cartilage or membrane; but in no instance in the body are they formed on a pulp. 

 The substance of the tooth must therefore be considered as distinct from bone 

 and may be ranked, both from its structure and mode of formation, as a species 

 of ivory.* 



* The tusks of the elephant are formed on a pulp, similar to teeth. Tumors are sometimes met with 



