The Teeth 315 



Sometimes there is a distension of the follicle with fluid, ac- 

 companied b)' a growth of cement upon its inner surface, giving 

 rise to what we know as compound follicular cysts. 



At other times the walls of the tooth follicle become greatly 

 thickened b}^ an abnormal growth of connective tissue, to con- 

 stitute what is known as a fibrous odontome. 



Finally, in the horse, and to a less extent in other animals, 

 where there are deep invaginations from the sides or upon the 

 crown of the enamel organ into the dental papilla, there is 

 normally formed in the grinders a sufficient amount of cement 

 to completely close the spaces between the infolded layers of 

 enamel. In some instances this formation of cement is in- 

 complete and an opening is left through the central portion of 

 this substance, from the grinding surface of the tooth down to 

 the bottom of the infundibulum, in close contact with the 

 enamel. Through this cleft, food particles pass and, becoming 

 lodged in the deepest part, undergo bacterial decomposition, 

 which causes a solution of the enamel and dentine and, finally, a 

 perforation of the pulp cavity, leading to a purulent inflamma- 

 tion of the tooth pulp and a destruction of the life of the organ, 

 with many complications of a highly important character. See 

 C Figs. 45 and 46. 



The enamel organ is subject to aberrations in its develop- 

 ment by which a tumor is formed, which may prevent the 

 eruption of the tooth and lead to what is known as a multilocular 

 cvst. 



Fig. 47. Cross section of molar 

 of adult horse. 



C, External cement. C, Cen- 

 tral cement. E, External 

 enamel. E^, Central enamel. 

 P, Pulp cavit}' surrounded 

 by dentine. 



The dental papilla may undergo two important forms of fetal 

 aberration or arrest in development. First, there ma^' be an ex- 

 cessive development of the dentinal substance to constitute an 



