XXXI IVORY 



391 



tion will reveal a very narrow ceutval area filled with 

 irregular liard tissue reiiresentiug the remains of a 

 central canal. In the living animal the large hasal 

 cavity is filled with living tissue known as the pulp : 

 it contains, among other things, l)lood -vessels and nerves. 

 The walls of the pulp chainher are lined with a layer of 

 cells (odontoljlasts) which are concerned in forming the 

 dentine (or ivory). Under normal conditions the active 

 formation of dentine continues as long as the elephant 

 lives, so that whilst the tusk is l)eing worn down at 

 the tip by use, it is continually renewed Ijy the odonto- 

 blastic cells in the pulp chamber. 



It occasionally happens that the pulp Ijecomes dis- 

 turbed by inflammation which maybe caused by injury, 

 such as fracture of the tusks l)y fighting, by musket 

 balls, by spears or some such contrivances used by the 

 natives for the destruction of the elephant. Interfer- 

 ence in a violent form with the pulp has a detrimental 

 efl'ect on the formation of ivory which is of some interest. 

 Sportsmen who hunt the African elephant endeavour 

 to kill this animal with what is known as a heart shot. 

 This may be effected l_)y shooting it through tlie 

 shoulder, or by a shot directed into the chest from the 

 front. In some circumstances the hunter must take his 

 chance of what is known as the forehead shot, and 

 occasionally the IjuUet penetrates to the brain. A more 

 reliable method of reaching the brain is to aim at the 

 centre of a line drawn from the eye to the ear-hole. A 

 liullet entering at this spot is always fatal. A l^ullet 

 badly aimed at an elephant's head is very lialile to 

 embed itself in the large pulp cavity of a tusk and 

 the elephant escapes death. In such an event the 

 pulp continues to form ivory and as a consequence of the 

 irritation caused by the presence of the foreign body, 

 the hard material which forms around the bullet differs 

 from true ivory and is known as secondary dentine. 



Ivory turners have known for more than a century 



