212 E VOL UTION AND DISEASE. 



In snakes the teeth do not come directly in contact 

 with the osseous tissue of the jaw ; but, coincident with 

 the development of the teeth, a formation of loose, bony 

 matter occurs, whereby the base of each tooth is firmly 

 cemented to the jaw-bone. Charles Tomes aptly de- 

 scribes this intermediate tissue as "bone of attachment"; 

 it is of loose and open texture, resembling the alveolus. 

 If from any cause this bone of attachment is softened or 

 absorbed the teeth fall. It happens that snakes living 

 in confinement are liable to a disease which induces 

 softening of the bones of the skull, and as the bone 

 which attaches the teeth to the jaw is, especially when 

 compared with the bones of the skeleton generally 

 which are of almost ivory-like hardness soft, and easily 

 absorbed, the snake in consequence loses its teeth. 

 The relation of tooth, jaw, and bone of attachment is 

 represented in fig. 1 1 3. Premature shedding of teeth 

 from this cause is not infrequent in snakes living in 

 captivity ; but I am unaware of its occurrence in snakes 

 living wild. 



Absorption of the alveolus occurs in mammals as age 

 advances, leading to the edentulous condition of the 

 gums which is one of the concomitants of advanced life ; 

 but the fall of teeth referred to in the case of the snake 

 is due to constitutional defects, and not old age. 



