520 PHILOSOPHICAL TRANSACTIONS. [ANNO 17QQ. 



The teeth of the elephant differ from those just described, in being composed of 

 a great many flattened oval processes ; these, while growing, are detached ; but 

 when completely formed, their bases unite together, and make the body of the 

 tooth, to which the fangs are afterwards added; and as the fangs are lengthened, 

 the tooth rises in the jaw. This is what may be considered as the tooth itself, be- 

 ing composed of the same materials as the teeth of carnivorous animals; but in 

 addition there is another substance, which unites all the processes together laterally, 

 into one mass; this is softer than the substance of the tooth, and on examination 

 proves to be similar, in its texture and formation, to common bone. As teeth have 

 been hitherto considered of the same texture with common bone; it is probable 

 that nothing but the 1 substances being united in the same mass, could have led 

 me to the discovery of their differing materially from each other. It will therefore 

 be proper to explain, in this place, the circumstances which first gave me the pre- 

 sent view of the subject. 



To obtain an accurate knowledge of the different parts of the elephant's tooth, 

 a longitudinal section was made, of one that was full grown. This section exposed 

 the lateral connection between the different processes, and the intermediate sub- 

 stance which unites them into one mass; it also showed the mode in which the 

 processes are continued into the body of the tooth and fangs. That the internal 

 structure might be made more distinct, the surface of this section was polished very 

 highly, which led to the discovery of the processes of the tooth having a more 

 compact texture than the intermediate substance; for though both had the same 

 appearance after being sawn, the processes bore a polish, which the other did not,* 

 and were laminated, like ivory ; while the other parts were porous, like the internal 

 structure of common bone. This led me to examine preparations of the elephant's 

 teeth, in a growing state, preserved in spirit, which explained the mode of growth 

 of these 2 substances to be different. In these preparations it was found, that the 

 processes of the tooth, which may be called ivory, were all formed on so many por- 

 tions of one common pulp, which had its origin in the jaw; and that the interme- 

 diate substance, which may be called bone, was formed on a species of ligament 

 situated immediately under the gum, from which membranous elongations extended 

 into the spaces between the processes of the tooth. 



This structure of tooth is not peculiar to the elephant, but common to the teeth 

 of all animals whose food requires to be ground, or much bruised, before it is 



in the frontal sinuses of the human body, having a perfect resemblance to ivory; they have their origin 

 in the bony cavity of the sinus, and extend themselves into the orbit of the eye. Of these, I have seen 

 2 instances, and was unable, at the time, to account for them; but am now induced to believe they were 

 formed on vascular excrescences, growing from the lining of the sinuses, similar in their organization to 

 the pulps above-mentioned. — Orig. 



* A portion of the jaw itself bore the same degree of polish as the intermediate substance of the 

 tooth. The cells in the elephant's skull are no part of its common structure; they communicate freely 

 with the cavity of the tympanum, and are therefore appendages to the organ of hearing, which I shall 

 explain more fully on some future occasion. — Orig. 



