ANIMAL DENTISTRY. I73 



ture of the enamel covering, through which channel acids 

 and micro-organisms gain access to the sensitive parts of the 

 tooth. The acids dissolve the calcium salts as the micro- 

 organisms decompose the organic material, producing con- 

 jointly a gradual gnawing away of the substance. The 

 progress of disintegration is frequently arrested by the for- 

 mation of a protecting wall around the cavity not unlike the 

 pyogenic wall of an abscess of the soft tissues. This process 

 is due to the calcification of the intra-tubular substance of 

 the dentine. In other events it progresses until the entire 

 tooth has become destroyed. 



The acids responsible for the dissolution of the cal- 

 careous matter of the tooth reach the teeth by being in- 

 gested as such, or by the transformation of food products 

 into acid substances. The micro-organisms are the putrefac- 

 tive parasites which normally inhabit the mouth and which 

 only become pathogenic at the proper opportunity. Efforts 

 to isolate a specific organism have thus far failed. 



The predisposing causes are numerous. Impairment of 

 the general health during the period of dental evolution, 

 rickets, pregnancy, irregularities of the arcades, meat diet 

 and uncleanliness of the mouth are the chief conditions re- 

 sponsible for the disease. 



Susceptible animals. In man caries is the most common 

 of all pathological conditions. Few mature human beings 

 escape its ravages upon the teeth. It is essentially a disease 

 of mature life, although when the predisposing causes are 

 legion even the temporary teeth may be attacked to a re- 

 markable extent. In the domestic animals it is observed 

 occasionally in the old dog, hog and cat. Solipeds and 

 ruminants are comparatively free from caries. In these ani- 

 mals decay of the teeth takes the form of an inflammatory 

 disintegration. (Necrosis, see page 152). In rare cases the 

 dissolution of the herbivorous tooth may undergo a disin- 



