208 EVOLUTION AND DISEASE. 



or osteo-dentine, thus encysting the missile. In due 

 course this foreign body moves onward with the segment 

 of the tusk in which it is embedded, and eventually 

 comes to lie in the exserted portion of the tusk until it 

 is liberated by wear or the skill of the ivory-turner. 



The entrance of a bullet is readily understood. The 

 great force by which they are propelled carries them 

 easily through animal structures, but with spear-heads 

 it is rather different Mr. Charles Tomes z gives an 

 intelligible explanation of this condition in connection 

 with the head of a spear embedded in an elephant's tusk 

 preserved in the museum of the Odontological Society of 

 Great Britain. It is to be presumed that a heavily-loaded 

 spear was dropped by a native from a tree, with the 

 intention of its entering the brain, upon the elephant as 

 it was going to water. But in this case the spear pene- 

 trated the open base of the growing tusk, which looks 

 almost vertically upwards, and then the iron point 

 appears to have broken off. This did not destroy the 

 pulp, but the tooth continued to grow, and the iron 

 point, twenty centimetres long and four in width, became 

 so completely enclosed that there was nothing upon the 

 exterior of the tusk to indicate its presence. 



The museums of the Royal College of Surgeons, 

 England, and Odontological Society of Great Britain, 

 contain many excellent specimens of foreign bodies 

 embedded in the tusks and molar teeth of elephants, as 

 well as masses of osteo-dentine removed from tusks 

 apparently healthy. Osteo-dentine, in all respects 

 similar to that formed in tusks under diseased con- 



1 " Dental Anatomy," ist ed., p. 322. 



