ANIMAL DENTISTRY. 153 



closed infundibulum is the cause of more than 95 per cent of 

 the decayed molars of the horse. The crusta petrosa, which 

 should hermetically seal the infundibula, is found wanting 

 and thus leaves an entraiice channel for infectious matter. 

 The pulp is therefore the first structure to be involved in 

 the inflammatory process, from which source it traverses 

 through the apical foramena to the blood vessels, alveolar 

 periosteum and bone. In rare cases the infectious matter is 

 admitted directly to the alveolar periosteum through imper- 

 fect gums, the space between the teeth, or through the ex- 

 posure of the periosteum while shedding the temporary 

 predecessor. Cystic tumors located directly upon the root, 



Fig. 107. 

 Table View of Tooth Shown in Figure 106. 

 I, 2. Openings of the infundibula, through which food enters the tooth. 



atheromatous degeneration of the radicals of the superior 

 dental artery, and external violence are the determining 

 causes in a few instances. In these latter circumstances the 

 pulp is the last structure to be involved in the inflammatory 

 process. Systemic disturbances, especially a "ricket dia- 

 thesis" induced by organic diseases or poor quality or insuf- 

 ficient forage during the period of growth, are predisposing 

 influences. 



Pathological Anatomy: — Pulpitis, either primary or sec- 

 ondary, is the basis from which to study the decayed molar 

 of the horse. The disease process begins with pulpitis and 

 ends finally in self-extraction of the tooth. Between these 



