100 ENAMEL OF THE TEETH. 
Purkinje and Raschkow regarded each fibre of the enamel- 
membrane as an excretory organ, a little gland which secreted 
the enamel-fibre corresponding to it. With our altered views of 
the growth of unorganized ' tissues, however, this explanation, 
previously so plausible, loses much of its probability. Various 
other explanations might be offered in place of it, but I have 
not made suflicient observations to enable me to decide upon 
the correct one. Firstly, one might suppose the organic basis 
of the enamel-prisms to be cells, which are formed, and continue 
to grow independently upon the dental substance, having no 
other connexion with the prisms of the enamel-membrane than 
that the latter furnishes their cytoblastema. This explanation, 
however, would compel us to regard the remarkable accordance 
which exists between the prisms of the enamel-membrane and 
those of the enamel as an accidental circumstance. But we 
should be obliged to adopt such a view, if it could be proved 
that another peculiar substance intervened between the enamel- 
membrane and the enamel, and I have several times observed 
such an one on the molar teeth of swine. It is very soft and 
full of vesicles, having the appearance of a slag. I think 
Purkinje mentions it also, but I cannot find the precise passage 
at this moment. It lay between the enamel-membrane and 
the tooth, but I am not certain whether it was also present 
at those points where the formation of the enamel had already 
commenced, and whether, therefore, it actually interrupted the 
continuity of the enamel-membrane with the formed enamel. 
We might suppose, as a second explanation, that the enamel- 
prisms are uninterrupted continuations of the prisms of the 
enamel-membrane, which become filled towards one end with 
calcareous salts. This is a very improbable explanation, and 
the connexion between the two structures is of too loose a 
nature to warrant its adoption. A third, and as I am at pre- 
sent disposed to think the most probable, explanation is, that 
the prismatic cells of the enamel-membrane separate from it, 
and coalesce with the enamel already formed, while at the same 
time their cavities either become filled with calcareous salts, 
or they become ossified throughout their entire thickness, their 
cavity being previously filled with an organic substance. This 
explanation makes the formation of the enamel accord with 
' [The author appears to use this word as synonymous for “ non-vascular.”—TRANS. | 
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