486 



it has given rise to the inflammation of the pulp, and its consequent irregular conversion into 



osteodentine. 



Presented by Thomas Keate, Esq. 



2766. Three sections of the base of the tusk of an Elephant, with an irregular mass 

 of osteodentine filling up part of the pulp-cavity, in which mass is imbedded 

 a large iron slug. Presented by the Right Hon. Lord Denman. 



2767. A mass of osteodentine from the tusk of an Elephant, perforated by an irre- 

 gular central canal, in which some foreign body may have been contained. 



This specimen was transferred from the British Museum, but had neither number nor 

 history. 



Mus. Brit. 



2768. A portion of the diseased tusk of an Elephant. 



Presented by Sir P. de M. Grey Efferton, Bart., M.P. 



2769. Two thin transverse slices removed from one end of the preceding specimen, 

 showing the proportions and relative position of the ivory, cement and osteo- 

 dentine. Presented by Sir P. de M. Grey Egerton, Bart., M.P. 



Structure of the Molar Teeth of the Asiatic Elephant. 



2770. The last right upper molar. 



The molar teeth of the Elephant are remarkable for their great size, even in relation to the 

 bulk of the animal, and for the extreme complexity of their structure. The crown, of which 

 a great proportion is buried in the socket, and very little more than the grinding surface 

 appears above the gum, is deeply divided into a number of transverse perpendicular plates, 

 consisting each of a body of dentine, coated by a layer of enamel, and this by the less dense 

 bone-like substance which fills the interspaces of the enamelled plates, and here more especially 

 merits the name of ' cement,' since it binds together the several divisions of the crown before 

 they are fully formed and united by the confluence of their bases into a common body of 

 dentine. 



In this example the molar consists of twenty-two plates, and two or three, in course of 

 formation at the back part of the tooth, have been detached and lost. As the growth of each 

 plate begins at the summit, they remain detached, and like so many separate teeth or denticles, 

 until their base is completed, when it becomes blended with the bases of contiguous plates to 

 form the common body of the crown of the complex tooth, from which the roots are next 

 developed. The lateral margins of the plates are rounded, and, though covered by a thick 

 cement, still project so as to give a vertically ribbed surface to the sides of the complex molar. 



The formation of each grinder begins with the summits of the anterior plate, and the rest 



