of the contiguous cell in the next central layer ; the angles at
■ which the elongated nuclei or successive portions of the dentinal
tuhuli thus unite constitute the secondary gyrations or curves of
those cells. The primary curves depend upon the arrangement of
the primary linear series of the parent-cells.
The original contour of these cells is most discernible after
calcification in the teeth of the Mammalian class, and here with
different degrees of distinctness in different species. They are
the true dentinal cells, and must not be confounded with the so
called ‘ intertubular or interfibrous cells’, the first notice of which
is due to Retzius.(l) The diameter of the dentinal or calcified
(1) The able Translator of “Müller’s Physiology,” Part I, 2nd. Edit., p. 431, gives the fact
that the substance between the tubuli of the ivory is composed of distinct cells, some of which
contain smaller cells, on the authority of a “ Report of the Meeting of the British Association,”
Athenaeum, No. 620, 1839. Retzius (“ Mikroskopiska undersôkningar ofver Tandemes, sardeles
Tandbenets, struktur,” 8vo. 1837, passim) describes the intertubular cells in the dentine of several
of the animal’s teeth which he examined. In the molar of the Hog, for example, he says :
“ short branches proceed from the sides of the main tubes throughout their whole extent,
some of which terminate in dilated ends, like cells and a little further on : “ only a few opake
cellules” (kalk celler) “ were visible in the interspaces of the tubes,” fpp. 33 & 34.) In the
molar of a Rhinoceros, Retzius saw many of the lateral branches of the dentinal tubes
terminating in large cells :—“ These cells,” he says, “ were thinly arranged in the intertubular
spaces,” (af bvilka mânga tydligen syntes sluta sig i stora kalk celler; dessa lâgo glest kring
spridda i stamrorens mellanrum) p. 32. M. Serres in his Report on certain Microscopic
preparations, submitted by Mr. Nasmyth to the French Academy, in proof of his discovery of
the intertubular cells, says of four sections from the teeth of the Megalichthys, Lamna,
Cachalot, and Elk “ Sur ces preparations et sous un grossissement de deux à quatre cents
diamètres on distingue entre les fibres dont l’ivoire se compose, des aréoles nombreuses
à parois distinctes.” He verifies this-as the “ fait capital du travail de M. Nasmyth,” and
gives it the character of novelty by contrasting it with an alleged opinion of Retzius, whom
M. Serres affirms to have regarded the intertubular tissue (tissue interfibreux) as amorphous !
(‘Compte Rendu de Seance de l’Académie des Sciences,’ 5 Décembre, 1842, p. 1055.) On
what authority M. Serres cites me (loc. cit. pp. 1056 & 1057) as contending for the
priority of the discovery of the intertubular, or interfibrous cells, I know not : he does not
primary cells of the pulp is usually one fourth or one half larger,
than that of the blood-disc of the species manifesting them. These
cells are figured, in the present Work, in the molar of the Mylodon
(PI. 79), in the incisive tusk of the Dugong (PL 95), in the premolar
(PI. 113) and the canine (PI. 113 a) of the Pteropus, in
the incisor of the Chimpanzee (PI. 119 a), and of the Human
Subject (PI. 123), and in the molar of a Rhinoceros PI. 139. In
the calcification of the dentinal pulp the thin transparent membrane
which covers the free surface, or that in contact with the enamel-
pulp, is the first to receive or become impregnated with the
hardening salts; and hence has been called the ‘ preformative
membrane.’ But at this early stage the calcifying membrane
vields to the pressure of the ends of the prismatic cells of the
enamel pulp, which are, likewise, beginning to take from the
surrounding plasma the hardening salts and impact them in their
interior. Thus are formed the pits upon the outer surface of the
coronal dentine of enamel-covered teeth, by which the enamel gains
a firmer mechanical connection with the dentine. As the process
of calcification of the multi-nucleated cells of the dentinal pulp
extends in its centripetal course, the pulp, in most teeth, progresrefer
to any publication of mine from which he derived the idea. I describe the intertubular
cells in many of the subjects of my “ Memoir” in the ‘ Transactions of the British Association,’
1838. In Ptychodus, for example: “ The interspaces of the canals are also occupied
by the same minute anastomosing reticulate tube-work. Numerous minute calcigerous cells
are also present in the interspaces,” p. 140. But instead of putting forth this as a discovery,
and misrepresenting Retzius as describing those interspaces to be amorphous, I premise by citing
Retzius’s discovery “ of the cells in the clear interspaces of the tubes,” p. 136. The true
dentinal cells, a figure of which in the tooth of the Mylodon was published in the 2nd Part
of this Work, PI. 79, in 1840, are very different from the intertubular cells on which M. Serres
reports. In most animals they include many tubes and intertubular spaces, and it is much
more exact to say that those cells include a tubular structure, than that the intertubular
space is cellular.