XXXI 
IVORY 
391 
tion will reveal a very narrow central area filled with 
irregular hard tissue representing the remains of a 
central canal. In the living animal the large basal 
cavity is filled with living tissue known as the pulp : 
it contains, among other things, blood-vessels and nerves. 
The walls of the pulp chamber are lined with a layer of 
cells (odontoblasts) 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 being worn down at 
the tip by use, it is continually renewed by the odonto¬ 
blastic cells in the pulp chamber. 
It occasionally happens that the pulp becomes dis¬ 
turbed by inflammation which maybe caused by injury, 
such as fracture of the tusks by fighting, by musket 
balls, by spears or some such contrivances used by bhe 
natives for the destruction of the elephant. Interfer¬ 
ence in a violent form with the pulp has a detrimental 
effect on the formation of ivory which is of some interest. 
Sportsmen who hunt the African elephant endeavour 
bo kill this animal with what is known as a heart shot. 
This may be effected by shooting it through the 
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 bullet 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 
bullet entering at this spot is always fatal. A bullet 
badly aimed at an elephant’s head is very liable 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 
