REVIEW—THE HORSE’S MOUTH. 
359 
process has been properly described. When the crown of the 
tooth first appears in the mouth, the fang is not completed, and the 
root has not even been developed. The horse is seven years old 
before all the roots are perfected, and when these are completed, I 
doubt if the after-growth is material. If the jaw of an old horse 
be examined, the alveolar cavities will be found to be shallow, 
shewing that the loss, consequent upon the wear, was compensated 
by the tooth being projected into the mouth, and not by any 
increase of substance. Again, those animals the incisors of which 
retain the marks in extreme old age, may shew long teeth, but not 
of that excessive length which growth would suppose ; only such 
as the want of wear would occasion, supposing the increase to 
cease when the root was perfected. The fang, in fact, is so much 
tooth in reserve, and as such answers the purpose for which 
growth was supposed to be necessitated. I have by me specimens 
of old teeth, but the measurement of none of them contradicts the 
opinion I have advanced, there being but a material increase of 
the crusta petrosa, which at the root blends with the ivory, and 
cannot be clearly separated from it. The thickening of the crusta 
petrosa around the root and neck, probably, never ceases during the 
health of the animal; but to this substance alone is confined the 
imaginary growth of the horse’s teeth. When the roots are per¬ 
fected, the length of the tooth is completed, and the only after 
process consists in a gradual deposition of earthy matter within the 
body of the member, the bulk of which is defined. In old teeth, 
the ivory becomes very dense; and he who attempts to cut through 
an old and young tooth will be made aware of a contrast. The 
p.ulp in the teeth, after the formation of the root, gradually di¬ 
minishes and ultimately disappears, in consequence of the ossific 
deposition. In fact, when growth ceases, consolidation has taken 
place, and rendered its continuance no longer necessary.” 
With a hook of such interest before us we have been turning over 
leaf after leaf until we find we have extended this article as far as 
our space allotted to “ review” will admit; and, we might add, as 
far as is consistent with the lengthy extracts we have already 
made from the work. We have not touched upon—nor can we 
afford room to say any thing about—the important topics of “ the 
recognitions of the milk teeth;” “ the distinctions” between them 
and their successors; “ the various points which denote growth;” 
“ the indications of age ;” “ the mode in which the horse cuts his 
teeth,” and the periods at which they are cut; the alterations the 
permanent teeth undergo ; the tricks practised upon the temporary 
