212 
ON DISEASES OF THE DENTAL APPARATUS 
growing from their roots during the entire life ; and they continue, 
at the same time, their outward eruption, under the influence of 
this growth, in such a manner that the parts worn by the friction 
are incessantly renewed ; and that, during a very long time, the 
teeth can preserve, if not their form, at least their length. 
Here, again, is found the explanation of a great number of the 
alterations in the dental apparatus. 
10. Are the teeth living ? The solution of this question, ana- 
tomically considered, is difficult, since neither vessels nor nerves are 
said to exist in these structures ; but the facts furnished by physi- 
ology and pathology witness that these organs, endowed with a 
sensibility obscure in their normal state, can become the seat of 
the most exalted and dreadful pain in their pathological state. 
11. This sensibility, is it inherent in the dental substance itself, 
or does it reside exclusively in the pulp ? — an organ essentially 
nervous, in which the sensations could be transmitted through the 
ivory, so that they might even penetrate as far as the phodapho- 
lous tissue, through the thickness of the horn-like matter which en- 
velops it. This is a physiological point, of which a satisfactory 
solution remains yet to be given. 
12. Are the teeth the combined product of the secretion of the 
pulp, and of the membrane which lines the alveolar cavities? 
We are inclined to think so, and some facts which we are about 
to produce will aid us to support this opinion. 
Having cursorily reviewed these few anatomical considerations 
necessary to the interpretation of clinical facts, we shall next con- 
sider the pathological part of our subject. 
The dental arcades of either the superior or inferior maxilla may 
be the seat of anomalies, of alterations, or of diseases, which place 
an obstacle, more or less complete, to the perfection of mastication ; 
and which have for results, either definite, approaching, or distant, 
the production of general alterations in the economy, consequences 
of an imperfect or insufficient nutrition. 
Let us study the alterations in the dental apparatus in the order 
of their gravity : — 
1. Anomalies in the Number of the Teeth. — Sometimes, but 
very rarely, we meet with supernumerary molars in the horse. 
This anomaly may be caused either by the persistence of the tem- 
porary teeth, by the development on one or both the branches of 
the arcades, and of the repetition of a greater number of permanent 
teeth than should naturally exist : in the latter case it is necessary 
to admit the existence of a greater number of dental bulbs than is 
usual and normal. 
We remember to have seen some time ago, at the consultation 
of the Veterinary College of Alfort, a horse which, to use the words 
