222 RAINEY, ON DENTAL TISSUES. 
stance is found partially filling up the opening in the fang. 
This, which resembles ordinary bone, is formed on a me n- 
branous matrix, directly contmuous with and similar in strue- 
ture to that of the dentine; and the primary particles are 
so like dentine-particles, as only to be distinguished from 
them by the manner in which they afterwards become 
arranged. These particles appear to coalesce in the same 
manner, but in the place of taking a rectilinear arrange- 
ment, they have somewhat of an arborescent form, the 
small spicular branchings of which anastomose, and inclose 
areole of a more or less circular form. These may be re- 
garded either as Haversian canals, lacune, or canaliculi, 
according to their size and shape, and the circumstance of 
their containing, or not, vessels; in which case they must 
of course be regarded as Haversian canals. As I have else- 
where described the structure and mode of formation of 
bone, I do not think it necessary to go further into this sub- 
ject. The crusta petrosa being considered by all anatomists 
as bone, I have called the vessels and epithelial corpuscles in 
contact with its matrix “the bone-pulp,’ and thus the 
analogy between bone and dentine is preserved; the pulp- 
cavity of a tooth corresponding to a true Haversian canal, 
the spaces between the dentine rods to the lacunz, and the 
extensions of these spaces between uncoalesced portions of 
dentine to the canaliculi of common bone. The enamel pre- 
sents similar analogies, but these are much less obvious 
and striking. 
In this paper I have, so far as I have gone, confined 
my observations to matters of rational inference, and such 
facts as can easily be verified by any one who will take 
the trouble, but my observations would be incomplete if 
something were not said of the functions of those parts which 
are indirectly concerned in the formation of the several 
structures which have been described. These are the dentine-, 
the enamel-, and the bone-pulps, and the part which has 
been designated membranous matrix. What I shall advance 
upon these points must of course be theoretical, and there- 
fore to be valued only according to its degree of probability. 
These pulps being composed of epithelial corpuscles (I prefer 
the term corpuscle to cell, as there is nothing hypothetical 
in its meaning), and abundantly supplied with vessels, as 
well as containing nerves, are doubtless the organs by which 
the materials composing the dental tissues are elaborated. 
Tt is observed in Kolliker’s ‘ Manual of Histology,’ that the 
reticulated connective tissue of the enamel-pulp contains 
in its meshes a great quantity of fluid rich in albumen 
and mucus. This fact I have myself noticed. And I have 
