DR. MARTIN BARKY’S RESEARCHES IN EMBRYOLOGY. 
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to continue, and give origin to others in their interior, the resulting substance might 
increase to an indefinite amount. May not this be the mode producing the intercel- 
lular — that is, the real — substance of cartilage? I am the more disposed to think 
this possible, from the fact that in the gill-cartilage of fishes, Schwann found the in- 
tercellular substance to consist of the closely aggregated walls of cells. 
394. Though ignorant of the precise nature of the process by which what were 
termed the divisions and subdivisions in the ovum were produced, I showed in my 
last memoir'f-', that it consisted in the origin of cells in cells; and suggested that it 
might admit of being extended to explain the increase of other cells. This opinion 
has been strengthened by the later observations, — which have enabled me in the pre- 
sent paper to communicate particularly the nature of the process, — as well as by the 
appearance of various cells incidentally observed. For instance, it has been very 
common to find the so-called epithelium-cells of the oviduct, filled with cells. Several 
of the varieties of these, some of them carrying cilia, are represented in Plate XXVIII. 
figs. 248 to 251. The cells of the so-called “disc” also (my tunica granulosa and 
retinacula), exhibit cells in their interior; and it is deserving of notice that in some 
instances the contained cells are only two in number (Plate XXVIII. figs. 245. y, 247-). 
But on a former occasion we saw that the ceils of which the entire embryo at certain 
periods is composed, are filled apparently with the foundations of other cells 
395. The experience of Professor Schwann, however, does not accord with these 
observations. He remarks §, “I have above mentioned an observation according to 
which, in the Tadpole, a young - epithelium-cell formed within another. This, however, 
is a very rare case, and in all the Vertebrata most epithelium-cells decidedly do not 
form as cells in cells, but in a minimum of cytoblastema exuding from the cutis.” 
And with reference to the experience of Schleiden, that in plants it is nearly or 
quite universal that new cells arise nowhere but in previously existing cells, Schwann 
remarks ||, “ In animals— the formation of cells in cells is the rarer case, but happens 
in so far as that a three to four-fold generation may successively form in one cell. — In 
cartilage by far the most cells arise in the cytoblastema [intercellular substance, see 
par. 393.] external to the cells already present 
f L. c., par. 314 to 317. J “ Second Series,” l. c., Plate VII. figs. 121 to 123, Plate VIII. fig. 150. 
§ L. c., p. 87. || L. c., p. 204. 
^ Judging from the delineations given by authors, I am more and more disposed to think the remarkable 
process of early development described in this memoir is in operation at all periods, and this for the production 
of morbid as well as healthy tissues. The process in question, as we have seen, consists first, in the founda- 
tions of young cells arising apparently in no other way than by divisions of the nucleus of a mother-cell, and 
secondly in the complete evolution of only two young cells, out of myriads which form. (The number con- 
tinuing may in some instances be several; these two occupying a central situation.) That this process is not 
peculiar to the period which I have investigated, we have evidence I think in Schwann’s delineations of the 
cells of cartilage (/. c., tab. I. figs. 8. 9.) before referred to; and in figures by Valentin of ganglion-globules 
(Ueber die Scheiden der Ganglien-Kugeln und deren Fortsetzungen, in Muller’s Archiv, 1839, ii. p. 139. 
taf. VI. fig. 1. a, b, e.). And that it is not peculiar to healthy structures, is shown, I think, in some of the de- 
lineations given by Muller of morbid growths. (Ueber den feineren Bau und die Formen der Krankhaften 
