Descending, as cells thus do, from an original mother-cell, and this by cleavage of the nucleus of that mother-cell, and all subsequent nuclei being propagated in the same way, by fissiparous generation,—such being the process, every nucleus or particle of hyaline is a sort of centre, inheriting more or less of the properties of the original nucleus, the germinal spot of the fecundated ovum ; and exercising an assimilative power. (The corpuscles of the blood are floating centres of assimilation.)

I wish it to be distinctly understood, that, in my researches, I always endeavoured to keep strictly to observation, avoiding all theory; and it may be here remarked, that some of those on the divisions in the ovum, just referred to, were made before I knew much of cells. Of one kind of animal alone, the Rabbit, about 150 were sacrificed in these observations; some of the most important of which I had the opportunity of enabling my honoured friend Professor Owen to confirm, by submitting the objects under the microscope to his practised and most rigorously scrutinizing eye.

How satisfactory now to find my observations confirmed by researches subsequently made by others. Thus the younger of the brothers Goodsir has since found, in the ovum of a cystic entozoon,* the germinal vesicle to fill with cells from the germinal spot, by a process obviously the same as that which I had described in the ovum of the Mammal; the germinal vesicle enlarging so as to occupy the entire ovum. Compare in Plate I., figs. 45 and 46; and read the description of the latter figure.

Farther, how satisfactory now to find those observations of mine adopted and formally applied in various departments

to that of the elliptical disc, and, of course, quite as general; viz., the globular, for every disc (cytoblast) appears to have once been a pellucid globule of hyaline. No observer can learn the structure of the blood-corpuscles, who does not carefully investigate their mode of origin; and this, not in blood taken from large vessels, which are merely channels for conveying it, but in that contained, and almost at rest, in the capillaries, and especially in the capillary plexuses and dilatations.

* Cœnurus cerebralis. Trans. Royal Society, Edinburgh. 1844. Vol. xv., Pl. xvi.

of physiology; for instance, by Professor Goodsir, who thereby makes a plain pathway through some of its most hidden regions. Thus for example it is that, regarding every nucleus in his germinal membrane (Bowman's basement membrane) as a germinal spot, and keeping in view what he denominates "that most important observation of Martin Barry on the function of the nucleus in cellular development," he is enabled to shew, that epithelium cells have their origin in the nuclei of that membrane,-an acknowledgment to me the more valuable, from the fact, discovered by Goodsir, in the ducts of glands, that the epithelium cell is the secreting organ.

This brings me to notice a chapter by the same author, entitled "Centres of Nutrition," regarding which he writes as follows:-" The phenomena presented by these centres incline me to regard them as destined to draw from the capillary vessels, or from other sources, the materials of nutrition, and to distribute them by development to each organ or texture after its kind. In this way, they are to be considered centres of germination; and I have elsewhere named them germinal spots, adopting the latter term from the embryologists. The centre of nutrition with which we are most familiar, is that from which the whole organism derives its origin-the germinal spot of the ovum. From this all the other centres are derived, either mediately or immediately; and in directions, numbers, and arrangements, which induce the configuration and structure of the being."t

That I can have no hesitation in admitting all the attractive force here attributed by Professor Goodsir to those centres, is obvious from its having been myself, I suppose, who made known the fact, that "the whole organism derives its origin from the germinal spot of the ovum;” and from what I wrote six years ago on the subject of centres in general. Thus, in the Philosophical Transactions for 1841, p. 201, will be found the following words, already quoted,— resulting, it will be seen, from my conviction that the germinal spot process, described by myself, was the same in all

* Anatomical and Pathological Observations by John Goodsir, F.R.S.E., &c. and H. D. S. Goodsir, M.W.S. 1845.

† Loc. cit., p. 1.

cells. I said, "It will be remarkable if the mammiferous ovum, which, because of its minuteness and the difficulty of obtaining it, had been considered beyond the reach of satisfactory observation, should now become the means of studying, not merely other ova, but certain processes by which nourishment is communicated, and the growth of the body effected at all future periods of life. Such, however, I think will really be the case."

As affording probability that this anticipation would be realized, I figured centres, special centres, of reproduction and assimilation; directing attention more particularly to such centres as were situated in the walls of tubes,-as, for instance, in those

Fig. 26.

reason for thinking it not unimportant that the contents of the 'primitive' cell and those of the secondary' cylinder should have their origin in the nucleus."* And subsequently, when those centres were referred to, my views regarding them were stated in the following words:

Fig. 27.

-"I conceive them to be centres of assimilation; having been led to this opinion by observing, in the first place, that they present the remarkable orifice in question; and, secondly, that they are reproduced by self-division. They descend in this manner from the nuclei of the original cells of development, i.e. from the nuclei of the corpuscles of the blood. That they are the source of new substance is very obvious; for they may be seen either unwinding into a filament, or becoming spindle-shaped to form one. But what I wish to

*Phil. Trans., 1841, p. 236.

6

add is, that the origin of new filaments in these nuclei appears to me to have especial reference to that assimilation of which they seem to be the centres. Although every nucleus seems to possess a reproductive property, there are thus special centres of reproduction. Such centres were also particularly indicated in one of my former memoirs,* as existing in the epithelium, the pigmentum nigrum, cellular' tissue, and cartilage. In describing the first origin of muscle, nerve, and the crystalline lens, also, I directed attention to such centres, stating that we might hereafter see reason for thinking it not unimportant that the contents of the 'primitive' cell, and those of the 'secondary' cylinder, should have their origin in the nucleus; and I was particularly desirous of connecting this fact with the existence of the orifice in question. It will now be seen that I had in view the subject of assimilation now referred to."†

Such, then, having been my views long since, I can have no hesitation in admitting all the attractive force attributed to those centres by Professor Goodsir; whose theory of nutrition, indeed, harmonizes so fully therewith, that a friend pointed it out to me as the formal application of my views. And on a perusal of the important volume just referred to, by the brothers Goodsir, I have the satisfaction to find, that all in it relating to the "function of the nucleus in cellular development," appears to be derived from the same source.

I have here great pleasure in acknowledging that Professor Goodsir's discovery of the real structure of basement membrane, appears to me an important step towards a solution of the question-How do the corpuscles of the blood enter into the formation of structures arising on the "free surfaces of parts or organs"? That the blood-corpuscles do enter into the formation of such structures, I must take to myself the credit of having shewn, by tracing them into the incipient chorion in the Fallopian tube. But it is now possible, I think, to offer an explanation of the mode in which they are

Phil. Trans., 1841, par. 119, 120, 135, 144.

† Edinburgh New Philosophical Journal, October 1, 1843, pp. 207, 208. On the Corpuscles of the Blood, Phil. Trans. 1840.

made to do so; which will be found at the end of this paper. I would here merely add that the discovery now referred to, is that of nuclei found by Goodsir in the basement membrane, the presence of which nuclei induced him to call that membrane a germinal membrane; for, adopting my views on the "function of the nucleus," he believes the nuclei in his germinal membrane to absorb from the capillaries on one side of that membrane, and give origin to the epithelium-cells on the other.

Here I must not omit to say, the orifice I have so generally met with in the nucleus, is most important in the function of absorption by that body, especially in centres such as those present in germinal membranes, fig. 50, and in the tubes, figs. 26 and 27; that orifice being in cells, as well as in certain of the Infusoria, a sort of mouth for nutrition; and in all it is equally an opening for fecundation, or what is equivalent to fecundation, for the introduction of a substance to be subjected to that assimilative process which prepares the cell for either reproduction or any other purpose. In tissuetubes, such as those in figs. 26 and 27, the nucleus with its orifice seems to remain for the purpose of exercising an appropriative power,-forming muscle in one instance, fibres of the lens in another, and so on.

Of the existence of the orifice in question, we have, I think, a highly interesting proof in observations made last year by Dr Harless;* who, in examining cells of the ganglion-globules in the lobus electricus of the Torpedo Galvanii, found nervous filaments connected with what he terms the nucleus of an inner cell. I have copied three of his figures; and if these be referred to, Plate I, fig. 44, it will be found that his nucleus of the inner cell is my orifice, situated in a and ẞ in a hyaline nucleus, membranous at the surface,† and in y in a finely granular nucleus or cytoblast,-being in the latter double. The nervous filaments so connected, and, as Dr Harless says, proceeding from the point in question, he describes as pellucid, and as belonging to the medulla of the primitive fibres. In some instances, he saw two such filaments connected with

α

*Müller's Archiv, 1846, No. III., p. 283.

†The "hollow nucleus" of Schwann,

VOL. XLIII. NO. LXXXVI.-OCTOBER 1847.