EXPLANATION OF THE PLATES. XI 



Fig. 9. The cavity of reserve sending off the pulp and sac of 



the wisdom tooth. 

 Fig. 10. The sac of the wisdom tooth advanced along a curved line 



into the maxillary tuberosity or coronoid process. 

 Fig. 11. The sac of the wisdom tooth returned to the extremity of 



the dental range. 



MUSKET-BULLETS IN TUSKS OF ELEPHANTS. 

 PLATE II. page 56. 



Fig. 1. A portion of a section of a wounded tusk ; a cement ; 5 regular 

 ivory deposited previous to the wound ; c irregular ivory 

 deposited after the wound. 



Fig. 2. A diagram illustrative of the mode of connection between the 

 Retzian tubes of the primary and secondary regular ivory, 

 and the cells and Retzian tubes of the different inosculating 

 systems of the irregular ivory, after inclosure of a ball ; a 

 cement with its osseous corpuscles ; b primary regular ivory 

 with its Retzian tubes ; c the ball ; d the irregular ivory 

 with its systems of tubes and cells ; e secondary regular ivory 



Fig. 3. A copper ball inclosed in a sphere of irregular ivory, on the 

 surface of which are the orifices of Haversian canals. Some 

 of the orifices have closed, and present the appearance of 

 irregular projections. The mass has begun to be attached to 

 the regular ivory of the tusk,, and would in time have been 

 inclosed in it. The ball must either have passed across from 

 the opposite side of the tusk, or must have sunk below the 

 level of the hole by which it entered. 



Fig. 4. Section of a tusk across the cavity of which a ball has passed, 

 and become inclosed in the ivory of the wall opposite the 

 hole by which it entered. The hole is filled with irregular 

 ivory, coated externally with cement. The cement over the ball 

 has been disarranged by the shock. This section proves that 

 the track of a ball across the pulp is not necessarily ossified. 



Fig. 5. Section of a tusk across the base of which a spear-head has 

 penetrated and remained in the wound. The weapon has 

 therefore been separated from the pulp by deposition of 

 irregular ivory in the form of a tube ; a cement ; b b ir- 

 regular ivory deposited previous to the wound ; c c regular 

 ivory deposited after the woimd ; d irregular ivory inclosing 

 a vacant space e, the seat of an abscess or sinus, and con- 

 tinuous with the cavity of /, a mass of irregular ivory (coated 

 with regular ivory) in the form of a tube surrounding the 

 foreign body. As irregular ivory always contracts in drying, 

 more than any other kind of dental substance, that portion 

 of the section marked g g has been bent outwards. 



Fig. 6. The same section viewed in profile ; a the broken shaft of the 



