314 STRUCTURE AND ADAPTATION OF TEETH 



dentine. The pulp then resuming its healthy- 

 state and functions, coats the surface of the en- 

 closing mass of osteodentine, together with the 

 rest of the conical cavity into which that mass 

 projects, with layers of normal ivory, closing the 

 breach in the thin parietes of the pulp cavity by 

 which the ball entered ; and as the growth of the 

 tusk proceeds, the ball so inclosed is carried 

 forwards into the solidified part of the tusk. The 

 occurrence of a spear-head in an elephant's tusk 

 may be similarly accounted for. The long axis of 

 the weapon corresponding to that of the cavity, 

 and no opening for its admission being discover- 

 able, it is evident that no human strength could 

 have driven such a body through solid ivory." 

 From the highly vascular structure of the pulp, 

 the tusks are slightly movable in the socket, and 

 occasionally, as in the case of the hippopotamus, 

 through irregular pressure on the alveolus, the 

 tusks take a spiral or other distorted form. "We 

 hear people speak of being driven nearly mad 

 with toothache ; but instances are recorded in 

 which the immensely large vascular pulp of the 

 elephant has been the seat of violent inflammation, 

 probably following mechanical injury, and un- 

 governable madness has been the result. A 

 painfully interesting account is given in Hone's 

 Every-Day Book of the destruction of a remark- 

 ably intelligent elephant at Exeter Change, in the 

 year 1826. The animal was attacked by pa- 



