60 ON THE MODE IN WHICH MUSKET-BULLETS BECOME 



on the surface of the pulp becoming solid from the deposition 

 of earthy salts in their walls and cavities. It is evident from 

 this that when a portion of the surface of the tusk-pulp is 

 destroyed by the passage of a ball, the formation of ivory at 

 that spot must cease. But we know that the formation of 

 irregular ivory commences, which indicates the existence of a 

 healing process in the pulp. The mode in which the wounded 

 pulp heals cannot be ascertained ; but it is accomplished pro- 

 bably by effusion and subsequent absorption of blood, depo- 

 sition of lymph, and regeneration of the peculiar tissue of the 

 pulp. So far this process is conjectural, but the irregular 

 ivory, formed by the regenerated pulp, is the subject of ob- 

 servation. When the ball passes quite across the pulp, the 

 track heals, but does not necessarily ossify, except in the im- 

 mediate neighbourhood of the ivory. 



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 ossi- 

 fication surrounding an abscess or sinus assumes the appear- 

 ance 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 microscope, it is seen to consist of a transparent 

 matrix, in which exist numerous medullary canals, showing 



