Microscopical Researches Into the Accordance in the Structure and Growth of Animals and Plants

by Theodor Schwann

THE SYDENHAM SOCIETY

INSTITUTED MDCCCXLIII

LONDON MDCCCXLVII

MICROSCOPICAL RESEARCHES

INTO THE

ACCORDANCE IN THE STRUCTURE AND GROWTH

OF

ANIMALS AND PLANTS

TRANSLATED FROM THE GERMAN

OF

DR. TH. SCHWANN

PROFESSOR IN THE UNIVERSITY OF LOUVAIN

ETC. ETC.

BY

HENRY SMITH

FELLOW OF THE ROYAL COLLEGE OF SURGEONS OF ENGLAND

SURGEON OF THE ROYAL GENERAL DISPENSARY, ALDERSGATE STREET.

LONDON

PRINTED FOR THE SYDENHAM SOCIETY

MDCCCXLVII.

C. AND J. ADLARD, PRINTERS

BARTHOLOMEW CLOSE.

TRANSLATOR’S PREFACE.

Any attempt on my part by way of introduction or commendation of Professor Schwann’s work, must, I feel, be altogether misplaced and unnecessary. The treatise has now been seven years before the public, has been most acutely investigated by those best competent to test its value, and the first physiologists of our day have judged the discoveries which it unfolds as worthy to be ranked amongst the most important steps by which the science of physiology has ever been advanced. The ROYAL SOCIETY OF LONDON has evinced its sense of the great merit of the work by awarding to its Author the COPLEY MEDAL for the year 1845. The extensive reputation and fully-acknowledged value of the original work, then, forbid my presuming that any one of my readers can be altogether unacquainted with it and the general outlines of the CELL-THEORY; I may, however, I trust, be permitted to add a few words respecting the edition which is now presented to the Subscribers of the Sydenham Society.

In the first place, I desire to tender my most unfeigned and unreserved apologies to the Council and Subscribers of the Society for the delay which has occurred in the issuing of this translation, and to assure the latter body that their TRANSLATOR’S PREFACE.

Council is in no degree responsible for its tardy appearance; when, nearly three years since, the Council did me the honour to accept an offer on my part to present to the Society a translation of Professor Schwann’s treatise, I fully hoped to have proceeded with so pleasing a labour without interruption or hinderance; but various unforeseen circumstances, both of a professional and domestic nature, have occurred to prevent the accomplishment of my object until the present moment.

I am greatly indebted to the Author for the labour which he has expended in revising his work for this translation. Amongst the most important advantages which this edition has derived from his revision, I may mention the addition of many notes illustrative of the text, and the amalgamation of the two papers on Cartilage and Ossification, which, as they were originally written and printed at a considerable interval of time, led to some difficulty in the comprehension of the Author’s precise views on that subject; and that circumstance is also to be received as explanatory of the appearance of some of the delineations of Cartilage in Plate III. It was originally intended to have added notes, which should bring down the history of the subject to the period of publication, but it was found that they would form a mass of material almost as large as the original text, and the idea was therefore abandoned.

In order that the reader might be in possession of the whole of the evidence upon which the Cell-Theory was originally based, I have appended a translation of Dr. SCHLEIDEN's Monograph so frequently referred to by our Author. TRANSLATOR’S PREFACE.

It is to be feared that many of my readers may consider an apology to be necessary on my part for the style of the translation, and think that I might have followed the German less closely with advantage; the nature of the subject, however, involving as it does such very minute descriptions, and the constant repetition of the same terms, added to the impossibility of doing justice to the Author’s close deductions in any other form than a literal translation, necessitated a much more rigid adherence to the original text, than I should have thought requisite under any other circumstances.

The Plates have been most faithfully copied from the originals by Mr. Henry Adlard.

HENRY SMITH. HENRIETTA STREET, CAVENDISH SQUARE; November 30th, 1847.

AUTHOR’S PREFACE.

It is one of the essential advantages of the present age, that the bond of union connecting the different branches of natural science is daily becoming more intimate, and it is to the contributions which they reciprocally afford each other that we are indebted for a great portion of the progress which the physical sciences have lately made. This circumstance therefore renders it so much the more remarkable, that, notwithstanding the many efforts of distinguished men, the anatomy and physiology of animals and plants should remain almost isolated, though advancing side by side, and that the conclusions deducible from the one department should admit only of a remote and extremely cautious application to the other. Of late, the two sciences have for the first time begun to be more and more intimately allied. The object of the present treatise is to prove the most intimate connexion of the two kingdoms of organic nature, from the similarity in the laws of development of the elementary parts of animals and plants.

The principal result of this investigation is, that one common principle of development forms the basis for every separate elementary particle of all organised bodies, just as all crystals, notwithstanding the diversity of their figures, are formed according to similar laws.I have endeavoured to explain the design of such a comparison more fully in the commencement of the third section of this treatise, and will now lay before the reader those data which are of most importance in an historical point of view in reference to the development of this idea. AUTHOR’S PREFACE.

As soon as the microscope was applied to the investigation of the structure of plants, the great simplicity of their structure, as compared with that of animals, necessarily attracted attention. Whilst plants appeared to be composed entirely of cells, the elementary particles of animals exhibited the greatest variety, and for the most part presented nothing at all in common with cells. This, harmonised with the opinion long since current, that the growth of animals, whose tissues are furnished with vessels, differed essentially from that of vegetables. An independent vitality was ascribed to the elementary particles of vegetables growing without vessels, they were regarded to a certain extent as individuals, which composed the entire plant; whilst, on the other hand, no such a view was taken of the elementary parts of animals. An essential difference both in the mode and in the fundamental powers of growth was thus maintained.

It soon, however, appeared that animal tissues do also occur which grow without vessels; for instance, in the formation of the ovum, and the earlier stages of development of the embryo previous to the formation of the blood; and, secondly, certain tissues of the adult, the epidermis for example. With respect to the ovum, which manifested indubitable proofs of an actual vitality, all physiologists were agreed in ascribing to it a so-called plant-like growth. This resemblance to the plant had reference to a growth of the conspicuous parts of the ovum without vessels, and was in no way connected with the form and mode of growth of the elementary particles. No one,however, considered that the analogy of the ovum entitled him to infer the operation of a plant-like growth of the elementary particles in the non-vascular tissues of the matured animal; on the contrary, the opinion rather gained ground, that these tissues originated and grew by means of a secretion from the surface of the organised tissues. Such was supposed to be the case with the epithelium, the crystalline lens, &c. This AUTHOR’S PREFACE.

opinion still maintained its ground, even when the structure of the tissues became more accurately known. Nor did the plant-like growth of the component parts of the ovum abolish the assumed essential difference of the growth of the vascular tissues.

A very important advance was made in the year 1837, when an actual growth of the elementary particles of epithelium was proved to take place without vessels. Henle (Symbole ad anatomiam vill. intest. Berol. 1837) showed that the cells in the superficial layers of epithelium are much more expanded than those in the deeper strata, a fact which leaves scarcely any doubt as to their true plant-like (i. e. non-vascular) growth. Henle ^[1] says (l. c. p. 9), “Hoe in loco (in planta pedis) cellularum (retis Malpighii) diametrum extrorsum augeri, saepius repetita observatione pro re certa affirmare audeo. Quas retis cellulas non minus in foetu suillo sensim increscentes transire in cellulas epidermidis, nunquam noninveni.” Purkinje and Raschkow (Meletem. circa mammal. dentium evol. Vratisl. 1835) had made the following observations upon the development of the epidermis: “In primis evolutionis periodis—squamule—epithelii nondum ita conformatae sunt ut in illa periodo, que partui praecedit, sed parenchyma plantarum cellulis simillimum ostendunt, cum quaeque squamula, quae postea talis apparet, tune temporis tanquam cellula polyedrica e membrana tenacissima constans globosamque guttulam continens in conspectum veniat. Pressu applicato rumpebantur istae cellulae atque lymphaticum liquorem effundebant, que cellulae, procedente evolutione, verisimile complanatz in illas polyedricas squamas mutantur.” Henle, when quoting this passage, adds (l. c. p. 9): “Haec illa num vero sola compressio in causa esse possit, ut parva cellula AUTHOR’S PREFACE.

in tantam laminam extendatur, nondum satis mihi constat: certe principio increscere volumen cellulze, nescio an imbibitione, constabit, nisi spes fallit, promotis disquisitionibus.” The caution with which Henle (and, indeed, every good physiologist) expresses himself in this passage with reference to the true growth of non-vascular tissues, is the best illustration of the state of the question. There is another observation of Henle’s, which is opposed to the epithelium being regarded as a lifeless substance secreted from the organised tissue; I allude to the passage (1. c. p. 22 et seq.) where he proves that the vibratile cilia, whose motion it is so difficult to explain by physical laws, stand upon little cylinders which are merely a modification of the epithelium.

Turpin (Annal. des Sciences natur. vu, p. 207) showed that the corpuscles, which Donné had found in vaginal discharges, and regarded as cast-off epithelium, were organised cells, and were in general oblong, and either pointed at one or both ends, or altogether irregular in figure, and that a new generation of spherical vesicles^[2] took place in their interior. He then remarks (1. c. p. 210): ‘On ne peut s’empécher, aprés avoir bien étudié les vésicules dont est formée la couche de mucus produite par la membrane muqueuse vaginale, d’y voir un tissu cellulaire bien organisé et composé comme tous les tissus cellulaires végétaux, d’un agglomérat, par simple contiguité, de vésicules distinctes et vivant individuellement chacune pour leur propre compte au dépens de eau muqueuse, qui les baigne de toutes parts.” Turpin then compares this tissue of animal cells, presented under the appearance of mucus, with what he calls “ suppurations végétales, excrétions muqueuses, qui semblent suinter sous forme de gouttelettes, de la surface des tissus vifs,’ and which is generally comprised under the AUTHOR’S PREFACE.

name of cambium ; and finally adds (1. c. p. 212), “En étendant ja comparaison entre deux choses si comparables, on trouve que la forme variable des vésicules du tissu cellulaire du mucus de la membrane vaginale, leur allongement en pointe, leur flaceidité, toujours entretenue par l'humidité constante qui baigne les tissus animaux, et le développement dans leur intérieur, soit des granules, soit des vésicules sphériques, sont toutes choses qui s’observent également dans la composition de tous les tissus cellulaires végétaux mous et aqueux, et que l’on désigne par le nom de pulpe ou de parenchyme dans certaines tiges ou feuilles grasses et dans certains fruits murs ou blettes.”

In the same year, Dumortier communicated researches into the development of the ova of snails. (Annal. des Sciences natur. vill, p. 129.) He observed, that in the mucus-globule, present in these ova, and from which the embryo is developed, there are generated cells, in the interior of which, secondary cells are formed, and so on, and that this tissue of cells becomes transformed into the liver, whilst the other tissues originate from a gelatinous mass, which exhibits myriads of points. In his conclusions, he says (l. c. p. 163), “En examinant l'évolution des Mollusques, nous avons démontré que les tissus animaux, quoique formés originairement de méme par la solidification des surfaces, se développent de différentes manières: le tissu cellulaire par des productions médianes, le tissu dermomusculaire par un feutré de canalicules centripétes. Ainsi, chez les animaux, les tissus ne se forment pas au dépens les uns des autres ; il n’y existe pas un tissu générateur unique, mais bic plusieurs tissus originairement distincts.—Les belles observations de M. Mirbel ont prouvé que chez les végétaux il existe un seul tissu originel, le tissu cellulaire, qui par une suite de métamorphoses, se transforme en tissu vasculaire. Par conséquent, le régne végétal est caractérisé par l'unité originel, et le regne animal par la pluralité originelle des tissus.” Vanbeneden and Windischmann give a different explanation to AUTHOR'S PREFACE.

these observations of Dumortier, in as much as they regard the tissue consisting of cells as the yolk and not the liver. (Bulletin de l’Acad. royale de Bruxelles, tom. v, No. 5.)

Other instances of the resemblance in form between different animal tissues and those of vegetables had already been repeatedly pointed out. Thus it was frequently said, in reference to thickly-crowded animal cells, or even mere globules, that they presented an appearance resembling vegetable cellular-tissue; and Valentin (Nov. Act. N. C. xvui, P. 1, 96), after describing the nucleus of the epidermal cells, states that it reminded him of the nucleus which occurs in the vegetable kingdom, in the cells of the epidermis, the pistil, &c. Nothing, however, resulted from such comparisons, because they were mere similarities in figure, between structures which present the greatest variety of form.

Schleiden instituted researches into the mode of development of vegetable cells, which illustrated the process most excellently. This admirable work appeared subsequently in the second part of Müller’s Archiv for 1838. He found, that in the formation of vegetable cells, small, sharply-defined granules are first generated in a granulous substance, and around them the cell nuclei (cytoblasts) are formed, which appear like granulous coagulations around the granules. The cytoblasts grow for a certain time, and then a minute transparent vesicle rises upon them, the young cell, so that, in the first instance, it is placed upon the cytoblast, like a watch-glass upon a watch. It then becomes expanded by growth. Schleiden communicated the results of his investigations to me, previous to their publication in October, 1837. The resemblance in form, which the chorda dorsalis, to which J. Müller had already drawn attention, andthe branchial cartilage of the tadpole present to vegetable cells, had previously struck me, but nothing resulted from it. The discoveries of Schleiden, however, led to more extend researches in another direction. AUTHOR’S PREFACE.

In the above-mentioned investigations of Henle, Turpin, and Dumortier, the resemblance which the animal tissues examined (epithelium and the liver or yelk of snails) bore to plants, lay, in the first place, in the circumstance, that their elementary particles grew without vessels, and in part, free in a fluid, or even inclosed in another cell; and in the second place, in that these elementary particles exhibiting a non-vascular growth, were furnished with a peculiar wall, like the cells of plants. When this coincidence was furnished, we were entitled to arrange these cells as near to the vegetable cells as the different kinds of animal cells, for instance, germinal vesicles, blood-corpuscles, and fat-cells, stand together, when regarded as different species comprised under the natural-history idea of cells.

The state of the matter, therefore, when I commenced my researches was as follows: The elementary particles of organised bodies presented the greatest variety of form; there was a resemblance between many of them, and, according to the greater or lesser degree of similarity, a group of fibres, of cells, of globules, and so on, might be distinguished, and in each of these divisions again there were different forms. As the cells taken collectively differed from the fibres, so also,only in a less degree, must the separate kinds of cells differ from each other, and the different kinds of fibres from each other. All those forms seemed to have nothing else in common, save that they grew by the addition of new molecules between those already existing, that they were living elements. So long as the epithelium-cells were regarded as a secretion of the organised substance, they could never, in that sense, be classed with the living elementary particles. There seemed to be no general rule with respect to the mode in which the molecules were joined together to form the living particles; here they united into one kind of cells, there into another, and at a third spot into a fibre, and so on. The principle of development appeared to be altogether different for such particles as differed AUTHOR’S PREFACE.

in their physiological signification ; and the diversity in the laws which it was necessary to assume in the development of a cell and a fibre, was also, only in a less degree, necessarily assumed between the different kinds of cells and the different sorts of fibres. Cells, fibres, &c. were therefore merely natural-history ideas, and no conclusion could be drawn from the mode of development of one kind of cell as to that of any other kind ; and, in fact, no such deductions were made, although we were acquainted with some important points in the process of development of certain kinds of cells ; for example, the blood-corpuscle (see p. 67 of this Treatise), and the ovum (see the Supplement, p. 217). Although the investigations quoted above determined the important fact of the non-vascular growth, they did not thereby effect any change in our views. The idea of proving the similarity of the principle of development for elementary particles which were physiologically different, by a comparison of animal cells with those of vegetables, was not contained in those researches, and with these, therefore, the investigators before mentioned might well come to a stand-still.

The discoveries of Schleiden made us more accurately acquainted with the process of development in the cells of plants. This process contained sufficient characteristic data to render a comparison of the animal cells in reference to a similar principle of development practicable. In this sense I com- pared the cells of cartilage and of the chorda dorsalis with vegetable cells, and found the most complete accordance. The discovery, upon which my inquiry was based, immediately lay in the perception of the principle contained in the proposition, that two elementary particles, physiologically different, may be developed in the same manner. For it follows, from the foregoing, that if we maintain the accordance of two kinds of cells in this sense, we are compelled to assume the same principle of development for all elementary particles, however dissimilar they may be, because the distinction between the other AUTHOR’S PREFACE.

particles and a cell differs only in degree from that which exists between two cells; so also the principle of development in the latter can only then be similar, when it repeats itself in the rest of the elementary particles. I therefore quickly asserted this position also, so soon as I was convinced of the accordance between the cells of cartilage and those of plants in this sense. It now became easy to accommodate the principle which I had laid down to the rest of the tissues, since the principle itself had already made me acquainted with the law of their development. Actual observation also completely confirmed the conclusion which had been drawn with respect to the rest of the tissues. It was not absolutely necessary that this principle should recur in the elementary particles of vascular tissues; for since no independent vitality of the elements, and therefore no diversity in the fundamental powers of growth, was assumed in their case, so, without prejudice to the principle, might they be subject to entirely different laws of development. But slight as was the probability at the commencement, that the principle could be carried out with respect to them, observation soon showed that vessels do not establish any essential difference in growth, but merely occasion some distinctions, which may be explained as the consequences of a more minute distribution of the nutrient fluid; of the change of material facilitated both by that means and by the circulation; and of a greater capacity of imbibition in the animal substance. Thus was the proposition firmly established by observation, that there is one common principle of development for the elementary particles of all organised bodies. It had already indeed been long known that all tissues were formed from a granulous mass; but that these granules bore some direct relation to the subsequent elementary particles, and what that relation might be was known in respect to but a few of the particles, and in them the mode of development appeared to differ so much, that unity neither AUTHOR’S PREFACE.

was nor could be recognised in it; for the conformity of the principle of development consists chiefly in the similar origin of these granules themselves, and this circumstance was not known, indeed the term granules or granulous mass was sometimes used to denote the entire cells, sometimes the nuclei, and sometimes granulous substances which form to a certain extent as chemical precipitates, and have no direct connexion with the elementary cells of organised bodies.

I communicated a preliminary review of the results gained, and which already comprehended most of the tissues, in the beginning of the year 1838, in Froriep’s ‘ Notizen,’ Nos. 91, 103, and 112. The detailed description required a longer time ; the first two portions of the present Treatise were placed before the Academy of Paris in August and December, 1838. J. Müller and Henle have already applied the theory to the most important pathological processes, and it now only requires to be extended to comparative anatomy, particularly amongst the lower animals.

At the conclusion of the Treatise I have attempted a theory of organisms, and for that purpose have excluded everything theoretical from the work itself, in order that facts might not be confused with hypothetical matter. The theory has at least this advantage, that by its aid any one may form a pre- cise idea for himself of the organic processes, which may conduct to new researches; such a theory may therefore be of use, even if assumed to be decidedly false. It contains the principles of the organic phenomena, both of the healthy and diseased organism. It was my intention to have added an application of the theory to the several organic processes;_ but circumstances compelled me to bring the work to a conclusion. Perhaps at some future time I may find opportunity to fill up the deficiency.

Berlin, March 1839.

CONTENTS.

PAGE

INTRODUCTION - 1

SECTION I. On the Structure and Growth of the Chorda Dorsalis and Cartilage - 10

1. Chorda dorsalis - ib.
2. Cartilage - 15

SECTION II.

On Cells as the Basis of all Tissues of the Animal Body - 36

• First division. On the ovum and germinal membrane - 40
• Second division. Permanent tissues of the animal body - 64

CLASS I. Isolated, independent cells. - 67

1. Lymph-corpuscles - ib.
2. Blood-corpuscles - ib.
3. Mucus-corpuscles - 70
4. Pus-corpuscles - 71

CLASS II. Independent cells united into continuous tissues - 73

1. Epithelium - ib.
2. The pigmentum nigrum - 77
3. Nails - 80
4. Hoofs - 81
5. Feathers - 82
6. The crystalline lens - 87

CLASS III. Tissues, in which the cell-walls have coalesced with each other, or with the intercellular substance - 96

1. Cartilage and bone -97
2. The teeth - ib.

CLASS IV. Fibre-cells, or tissues, which originate from cells that become elongated into bundles of fibres - 110

1. Areolar tissue - ib.
2. Fibrous tissue - 123
3. Elastic tissue - 124 CONTENTS.

CLASS V. Tissues generated from cells, the walls and cavities of which coalesce together

1. Muscle
2. Nerves :
3. Capillary vessels

SECTION III

Review of the previous researches — The formative process of Cells — The Cell-theory - 161

Survey of Cell-life - 168

Theory of the cells - 186

Supplement (vide page 46) on the signification of the germinal membrane -217

Remarks upon a statement put forth by Professor Valentin, respecting previous researches on the subject of this work - 219

Explanation of the Plates - 225

CONTRIBUTIONS TO PHYTOGENESIS, by Dr. M. J. SCHLEIDEN - 229

Description of Plates to do. - 265

1. Henle’s observations are detailed at page 76 of this treatise. The researches of Turpin and Dumortier could not be quoted, as I only became acquainted with them at the conclusion of my work.
2. May there not have been some confusion here with the nuclei of the epitheliumcells: At present, as far as regards Mammalia al least at least, we know of no formation of cells within cells in the epithelium.