Treatise Upon the Genesis and Development of the Dental Follicles to the Epoch of the Eruption of the Teeth. [Volume: 2, Issue: 9, April, 1861, pp. 475-486]

476

THE DENTAL COSMOS.

It is, as has been stated, near the sixtieth day of the human foetus that
the first follicle shows itself in the lower jaw, and about the sixty-fifth
day in the upper.
Thus the follicles do not appear at the same time in the two jaws, or
in either of them in particular; but the order in which they originate in
the one is reproduced in the other. This fact is observed in all the mammiferse; but in order to find which tooth is the first to appear in each of
them, it is necessary to make direct observations-for the reason that
in some of them it is an incisor, as in man; in others it is the canine, as
in the hog; or a molar, as among the ruminating animals. In the case
of the latter, this fact coincides with the absence of the incisors in the
upper jaw.
If we consider the order in which each of the constituent parts of the
follicle appear in particular, we will find that the bulb always originates
first; the wall very shortly after, but still a little after; and in the last
place, appears the organ of the enamel, as soon as the follicular wall is
closed.* In all of them the development of these constituent parts, and
consequently that of the follicle, is effected in the same order of similitude
and succession. It is in the follicle which appears first, that the follicular wall closes, the organ of the enamel appears, the ivory originates, and
the enamel after it. These phenomena are accomplished in the same
order in the second follicle, but a little later, and also in the others, in
every species of mammiferee or of tooth; we do not find that a follicle
originating before another is outrun by the latter in its primitive original
development. But it is important at present, that we should not confound
* M. Oudet and several other authors have said, that the parts first formed are
the membranes of the dental follicles, and that it is at a more advanced period, in
the course of the third month, that a small yellowish body, the pulp, is developed
at the extremity of the vessels of the follicle. This pulp, rising little by little, lifts
the internal membrane, which in this manner becomes its exterior envelope. (Oudet,
loc. cit., 1835, p. 98.) We will show that this opinion is incorrect. Raschkow is
also wrong in saying that the wall appears first, followed by a nucleus formed of
corpuscles or angular grains bound together by fibres; he names it the organ of the
enamel; and makes it originate before the bulb or dental germ. He remarks that
the wall is vascular from the beginning, especially on the side of the dental nerves
and vessels where its capillaries reach it. (Raschkow, meletemata circa mammalium
dentium evolutionena. Vratislavise, 1835, page 12.) M. Guillot admits that the
follicle originates by a mass which he calls the initial spheroid or primitive trace of
the teeth; that three distinct divisions rapidly appear in these spheroids by a sort
of partition. One of them is central, and he calls it the nucleus or noyau, a name of
ambiguous signification-it is the dental germ or organ of the ivory. The second
is situated around the other, and is the middle zone or organ of the enamel. The
exterior third one is organized in a fibrous sack when the germs of the ivory and
enamel have been for a long time formed in the generating part-later still, it becomes vascular. (Guillot, loc. cit., 1859, vol. ix. pp. 289 to 297.) It will be proved
hereafter that these phenomena do not occur in this manner.