# Microscopical Researches/Remarks

REMARKS
UPON A STATEMENT PUT FORTH BY PROFESSOR VALENTIN, RESPECTING PREVIOUS RESEARCHES ON THE SUBJECT OF THIS WORK.
AFTER I had finished this Treatise, I received the first part of Wagner’s ‘Lehrbuch der Physiologie,’ Leipzig, 1839; which was just then issuing from the press, and which contained (at page 182) an outline of the development of the animal tissues, communicated by Professor Valentin. The author introduces the subject with some historical remarks, in which he represents my researches as giving an essential completeness to the analogies between animal tissues and vegetable cells which had been previously pointed out, more particularly by himself. There are very many ways of drawing a comparison between two objects, and similitudes may be discovered which are opposed to the whole internal construction of the things in which they are observed. Everything, therefore, depends upon the sort of comparison drawn. If Valentin’s historical representation be justified, the idea of a comparison, similar in its kind to that on which my researches are based, must have a previous existence in his earlier investigations. I have endeavoured to analyse the fundamental idea of my investigation in the commencement of the Third Section of this treatise; it was this—that one common principle of development forms the basis of all the elementary particles of organisms. It originated in a comparison being drawn between a cartilage-cell and a vegetable cell, in such sense, that the molecules are united together for the formation of both of them, in accordance with similar laws, since in both instances a nucleolus is first formed; around this ​a nucleus, and around this again a cell. The accordance in the mode of development of two so different elementary particles, first led to the deduction of the principle of a similar mode of formation for all elementary particles, and then to its proof by observation. Therefore, what we have to decide is, first, whether the idea of comparing an animal elementary structure with a vegetable cell, with reference to a similar mode of development, does occur in Valentin’s earlier observations; and, secondly, whether Valentin has recognised the principle which is contained in the similar mode of development of two elementary particles which, in a physiological sense, are very dissimilar. In my preface I have given a brief historical sketch of the subject from my own point of view, and Valentin’s remarks do not convince me of the necessity of making any alteration in it. Impartiality, however, requires that Valentin’s representation should follow this statement, and I therefore append the passages cited by him, word for word, from his works:
“In my first histogenetic researches, I observed certain peculiar granules lying in a transparent gelatinous substance, as the primordial matter of all the tissues. I pointed out the difference between these granules in the serous and mucous layers, at the period of the earliest separation of the layers from one another. In the vascular layer I found large globules or cells, which, in respect to their form and juxtaposition, I compared, as early as the year 1835, with vegetable cellular tissue. (Entwickelungsgeschichte, 287. The vascular layer seems to be composed of large globules having a mean diameter of 0·001013 Paris inch, which are perfectly transparent in their interior, and so closely crowded together, that they are flattened against one another at many of their points of contact, and assume an hexagonal form like the cellular tissue of plants.) I also first directed attention to the resemblance in form of the cartilages in which ossification was commencing, and particularly (from observations made in conjunction with Purkinje) of the branchial cartilage of the tadpole to the vegetable cellular tissue. (Ib. 209-10. The cartilages of the labyrinth present a variety of form whilst passing through the process of ossification, which differs very essentially from most of the other cartilages of the body, which will be described at greater length presently. In place of the ordinary cartilage-corpuscle, they contain large bodies which are not so well defined in form, most of them furnished with linear boundaries, being roundish, ​ semilunar, tetrahedral, or polyhedral in shape, with a mean diameter of from 0·000405, to 0·000650 Paris inch. But so soon as they ossify, the calcifying portion, or that which is already ossified, consists of a tissue of beautiful six-sided prisms (Balken), closely resembling vegetable cellular tissue, upon and within which are small granules of a round figure, with a diameter of about 0·000152 Paris inch. The last described form, was observed both by Purkinje and myself long since in the cartilages of the tadpole also, especially in the branchial arches.)I described the round celis of the globules with their interposed cellular substance from the chorda dorsalis of young embryos. (Ib. 157. Although the external appearance of the chorda dorsalis clearly presents a certain resemblance to a cartilage, the microscopical investigation of its structure most distinctly disproves similarity. In every instance in which it is present, it consists of an external, symmetrical, perfectly transparent envelope and globules of variable size, but always very numerous, and lying closely packed together. A gelatinous and perfectly transparent mass occupies the interspaces left between them. These globules are largest in fishes and amphibia, smaller in birds, and smallest in mammalia.” In the second passage, which Valentin cites on this point (Repertor. i, 187), the researches of J. Müller, which I have noticed at page 7 in this treatise, are referred to and quoted, the following also is from the same source :—“ which (chorda dorsalis) the reporter (Valentin) has also observed in foetal pigs of eight lines in length, in the form of a thick cord lying within the cartilaginous vertebrae, its internal structure, in the embryos of mammalia, birds, and amphibia, being, according to his observations, essentially similar to the permanent analogous formations of the cartilaginous fishes.) Soon after this J. Müller, from his own independent investigations, gave a more detailed explanation of the cells in the spinal cord of fishes (Myxinoiden,74, &c.) In the epithelia, which Purkinje and Raschkow (Meletem. c. mammal. dent. evol. 12), as well as I (Nov. act. ac. N. C. vol. xvi, p. 1. 96) — — These (the tuft-like groups of the choroid plexus) do not lie free, but they, as well as the connecting granulous membrane, are covered with a very delicate and transparent epithelium, the separate globules of which have the most regular six-sided cell-border, and are perfectly colourless and transparent. Each of them, however, contains, in the mass in its interior, a dark round nucleus, or formation, which reminds the observer of the nucleus occurring in the cells of the epidermis, the pistil, &c., in the vegetable kingdom. In man, whose choroid plexus exhibits a more blackish or dark colour even to the naked eye, the epithelium itself has a similar formation to that just described, but the centre of each cell contains in its exterior a round pigment-globule, corresponding to the central point of the situation of the nucleus in its interior. Similar pigment-globules exist in most birds, but not being so regularly deposited, it is ​more difficult to detect the cell-shaped and more rounded globules, although they are quite as certainly present. When the object has not been at all damaged, the cells, and especially the pigment-globules adhering to the outside, exhibit an arrangement like that of the vegetable cells in general, and particularly in the earliest stages in the formation of the leaf, that is, a disposition corresponding to spiral lines projected on the surface in accordance with the strictest rules) —— compared to the cellular tissue of plants, I chose, expressly (l.c. 77. Each of these globules (ganglion-globules), wherever observed, has an external, more or less distinct, areolar tissue-like envelope, and contains a parenchymatous mass proper to itself, an independent nucleus or kernel (nucleus oder Kern), which again encloses a second roundish, transparent nucleus)——on account of this resemblance in form, the uniform appellation of the nucleus (Kernes), just as I afterwards described the nucleolus which was observed by me. (Repertor. i, 143. In every cell without exception there is a somewhat smaller and more compact nucleus of a round or oval form. It usually occupies the centre of each cell, consists of a minutely granulous substance, but encloses a well-defined, round corpuscle, which thus forms a sort of second nucleus within it.)In the study of the epithelia, prosecuted particularly by Henle and myself, there was no want of analogies with vegetable cellular tissue, the individuality of the cell-parietes was also distinctly demonstrated. (Ib. 284. Roundish, hexagonal, flat, and tolerably thin cells lie (in the external skin of the proteus) close upon one another, disposed in regular arrangement, and always connected together with their lateral edges and angles in mutual correspondence. The interior of these delicate bodies is filled by a granulous or yellowish mass, which represents a sort of nucleus. But the separate granules of this nucleus, however closely they may he together, may be accurately distinguished from one another. With a very strong magnifying power, each one of these granules may be seen to be more transparent in its centre than it is in its periphery. It may then also be most distinctly ascertained, that the somewhat delicate parietes of each cell are perfectly isolated from the central cavity. No trace of granules or fibres can be observed on the walls themselves; there is merely a clear, transparent, vitreous, and homogeneous mass.) I had also remarked that the nuclei (pigment-vesicles) were the parts first formed in the pigment of the choroid coat (Entwickelungsgeschichte, 194. The following is the mode in which, according to my observations, the stratum of pigment is formed in man, mammalia, and birds; separate, round, colourless, and transparent corpuscles are first deposited upon the internal surface of the substance they are to cover, in the earliest period (up to the tenth week) these corpuscles in the human subject measure from 0·000355 to 0·000405 Paris inch in diameter. They are the future pigment-corpuscles or pigment-vesicles. ​ Pigment-globules of a black colour are soon, however, developed on their periphery, so that the corpuscles or vesicles just mentioned are transparent in their centre when they have ceased to be so, and have become dark on their circumference. It is plain that von Ammon and R. Wagner have seen this condition as well as myself. The globules are so small from the commencement, that they ..... This process of deposition of the black-coloured globules upon the pigment-corpuscles goes on afterwards continuously, and to such an extent that the latter are enveloped and covered on all sides by them, and are only rendered visible when the globules are removed by pressure or washing.);——and I compared the pigment-cells with the cellular tissue of plants. (Repertor. ii, 245. The pigment here (in the choroid) has the same character which it has in most other parts of the body, that is, a round, clear, transparent, and colourless nucleus, or the pigment-molecules lie closely crowded together around a pigment-vesicle. These heaps of pigment composed of pigment-vesicles, and the molecules of pigment deposited around them, are extended out sidewise, and in man, the dog, the rabbit, the horse, the ox, and such like, form unequal pentagons or hexagons, which are placed close together in a similar manner to the cells of the parenchymatous cellular tissue of plants. Langenbeck de retina, 38.) Schwann gave an essential completeness to these analogies, by showing that the gelatinous primordial mass of the tissues was composed of cells, that the bodies imbedded init are nuclei, and that these and the cells often exhibit analogous laws of development. (Froriep’s Notizen, 1838, Mikroskopische Untersuchungen über die Struktur der Thiere und Pflanzen, Heft i, 1838.) As early as 1837 I had observed the cells of the germinal membrane in the ovum of sepia, with their nuclei and nucleoli, and the areas surrounding them, and had communicated my researches in a letter to Breschet. Shortly after I became acquainted with Schwann’s first communication I commenced the investigation of the subject. The chief results of my inquiries are contained in the following communication. I have, at the same time, referred to the corresponding passages in the first part of Schwann’s treatise, which I have received this day.”
I will only add that the second part also, (consisting of sheets 8 to 13, and Plates III and IV,) therefore the whole of the portion of my treatise containing the observations, had appeared previous to Valentin’s researches, and had been communicated to the Parisian Academy in the year 1838; a remark which does not appear altogether superfluous, since Professor Wagner has ​communicated an epitome of my observations (which I sent to him four weeks after he had requested it from me) in his Physiology, with the remark that it had arrived later than the observations of Valentin. Moreover, even my first communications in Froriep’s Notizen contained the fundamental laws for the formation of all the tissues, and the details also respecting by far the most of them.