20 



12. The enamel of the horse's tooth appears to be 

 unorganized, and to contain no animal matter. Hy- 

 drochloric acid entirely dissolves it with a slight effer- 

 vescence, and though a few and a very few threads 

 remain, these rather seem to be connexions between 

 the ivory and crusta petrosa, than component parts 

 of the enamel itself. That the enamel is an un- 

 organized substance, it may be essential to state, 

 is asserted only of this body in the tooth of the 

 horse ; for the enamel of the cow's tooth is of a 

 different nature, since hydrochloric acid does not 

 dissolve it, affect its whiteness, or destroy its form. 

 The enamel is the least of the three components of 

 the tooth ; of a whitish semi-transparent shining as- 

 pect, it forms a thin crust to the ivory, lying imme- 

 diately under the crusta petrosa, and extending nearly 

 to the root. 



13. The ivory forms the main bulk of the tooth, 

 and though blood vessels can be traced to, but not 

 within its substance, yet it presents numerous pores 

 or minute canals, radiating from the centre to the cir- 

 cumference, which the mind naturally associates with 

 nutrition. These pores cannot be traced to the 



