96 MR GOODSIR ON MUSKET-BULLETS FOUND IN THE TUSKS OF THE ELEPHANT. 



There are two exceptions, however, to the non-ossification of the track of the 

 ball, namely, the ossification which takes place round the bullet, and that which 

 occurs round the whole or any portion of the track, which may suppurate and 

 form a sinus or abscess. In both these cases deposition of irregular ivory takes 

 place, assuming the same characters as the irregular masses which appear at the 

 two extremities of the track of the ball through the pulp. 



The ossification round the ball generally assumes the form of a hollow sphere. 

 Its surface exhibits a number of holes (which are the orifices of medullary canals), 

 and these are occasionally prolonged through stalactitic-looking processes, which 

 lie in the direction of the axis of the tooth, The ossification surrounding an ab- 

 scess or sinus assumes the appearance of a shell of variable thickness, and directed 

 towards one or both of the shot-holes. 



When thin sections of this irregular ivory are examined under the micro- 

 scope, it is seen to consist of a transparent matrix, in which exist numerous me- 

 dullary canals, shewing traces of dried pulp in their interior. From these canals, 

 which correspond to the Haversian canals of true bone, secondary medullary ca- 

 nals, similar to those in the teeth of certain fishes, radiate. The sides and extre- 

 mities of these secondary medullary canals send off numerous minute tubes, which 

 are true Retzian tubes, and similar to those in the regular ivory, but not so closely 

 set. These Retzian tubes have a general radiating direction, and proceed in irregu- 

 lar wavy bundles, Avhich sweep past one another without mingling, but branching 

 particularly at their extremities. The great central medullary canals are very 

 numerous, and each of them has its own system of secondary canals and Ret- 

 zian tubes. 



These individual systems, when seen in a mass of irregular ivory, appear 

 globular or spindle-shaped ; when viewed in section, they resemble circular or 

 oval opaque spots with a hole in the centre. These individual systems, however, 

 are not isolated ; for they communicate, first, by means of the central canals, 

 which constitute an inosculating system ; and, secondly, by the ramifying extre- 

 mities of the Retzian tubes, which communicate through the medium of cells 

 more or less minute, and which are more numerous in some places than in others. 



The formation of the irregular ivory does not go on indefinitely : a limit is 

 set to its increase, and the changes which ensue at this stage of the process are 

 highly interesting. I have already mentioned the existence of the orifices of 

 Haversian, or medullary canals on the surface of the mass of irregular ivory. 

 When the further formation of this is to terminate, these orifices are gradually 

 closed, and appear like imperforated projections on the surface. It is evident, 

 therefore, that the inclosed vascular contents of the canals, that is to say, the 

 ramified processes of the tusk-pulp in the irregular ivory, are cut off from the sys- 

 tem. They dry up, and the formation of ivory in the interior ceases. The peri- 

 pheral surface of the irregular ivory is now, in reference to the general pulp, in 



