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FEBRUARY 20, 1858.
PHYSIOLOGICAL AND PATHOLOGICAL TISSUES.
The higher animal tissues: muscles, nerves, vessels, blood.
Muscles.—Striped and smooth.—Atrophy of.—The contractile substance
and contractility in general.—Cutis anserina and arrectores pili. Vessels.—Capillaries.—Contractile vessels.—Nerves.
Pathological tissues (Neoplasms), and their classification.—Import of vascularity.—Doctrine of specific elements.—Physiological types (reproduction). —Heterology (heterotopy, heterochrony, heterometry) and malignity.— Hypertrophy and hyperplasy.—Degeneration.—Criteria for prognosis.
Law of continuity.—Histological substitution and equivalents.—Physiological and pathological substitution.
In my last lecture I portrayed to you the first two groups of tissues, the one embracing epithelium or epidermis, and the other the different kinds of connective tissue. What still remains forms a somewhat heterogeneous group, the individual members of which do not, indeed, in the degree that is the case with epithelium and connective tissue, bear a real relationship to one another, yet, on the whole, present a certain correspondence, in that they constitute the higher animal structures, and are distinguished by their specific mode of development from the less highly organized epithelial and connective tissues. Moreover, most of them appear under the form of connected, more or less tubular, structures. If a comparison be instituted between muscles, nerves, and vessels, the idea very readily suggests itself that we have in all three structures to deal with real tubes, filled with now more, now less, moveable contents. But this notion, however well it may accord with a superficial view of the matter, does not express the whole truth, innsmuch as we cannot compare the contents of the different tubes.
The blood, which is contained in the vessels, cannot, at least at present, be regarded as analogous to the axiscylinder, or the medullary [white] substance of a nervetube, or to the contractile substance of a primitive muscular fasciculus (Muskelprimitivbundel [muscular fibre]). I must, indeed, here remark, that the original development of all the structures which may be included in this group is still a subject of great controversy, and that the view maintaining the simply cellular structure of most of these elements is by no means completely established. This much, however, appears to be certain, that, at any rate in foetal parts, the blood-corpuscles are just as much cells as the individual constituents of the walls of the vessels within which the blood flows; and that the vessel cannot be designated as a tube which invests the blood-corpuscles, as the cell-membrane does its contents. It is therefore necessary in the case of the vessels to draw a line between their contents and proper walls, and to repudiate the seeming resemblance between the vessels, and the nerves and muscular fibres. Again, if we wished to adopt the mode of origin of the several tissues as the basis of. our classification, we should, in accordance with prevailing views, have to associate the lymphatic glands also with the blood, and might be rather reminded of a connection such as we have seen to exist in the relations between the epidermis and the rete mucosum. But here I must once more impress upon you that the lymphatic glands are distinguished from glands properly so called, not only by their not possessing any excretory duct in the ordinary sense of the word, but also because from the mode of their development they by no means occupy the same position as ordinary glands, but are on the contrary at every period of their existence nearly allied to the connective tissues, and that,
THE HIGHER ANIMAL TISSUES. 51
therefore, the temptation would rather be to class them with the tissues which we see produced by the transformation of the connective tissues. Yet this would at the present moment be still rather a venturous undertaking.
Amongst all the forms of which we have here to treat, the elements of muscle have generally been regarded as the most simple. If we examine an ordinary red muscle (I do not say a voluntary one, inasmuch as in the heart also we meet with fibres of the same form) we Jiio 23
find it to be essentially composed of a number of cylinders, for the most part of equal thickness (primitive fascicidi [fibres]), which on a transverse section are seen to have a cylindrical form, and on which we at once perceive the well-known transverse striae, that is, broad lines which generally run transversely through the fasciculus with a somewhat wavy outline, and are almost as broad as the intervals that separate them. In addition to this transverse striation we also see, especially when certain modes of preparation have been adopted, stria? following a longitudinal direction, and these, indeed, in some preparations preponderate to such a degree, that the muscular fasciculus appears to be striated almost exclusively in this direction. If now we add acetic acid, there are forthwith disclosed immediately beneath the sheath, and now and then also more towards the centre, nuclei which are tolerably large,
Fig. 23. A group of primitive muscular fasciculi [fibres], a. The natural appearance of a fresh primitive fasciculus, with its transverse striaj (bands or discs), b. A fasciculus gently acted upon by acetic acid; the nuclei stand out distinctly, and in one of them two nucleoli are visible, whilst in another the division is complete, c. A fibre acted upon more strongly by acetic acid; the contents are swollen up at the end, so as to protrude from the sheath (sarcolemma). d. Patty atrophy. 300 diameters.
and mostly contain large nucleoli in greater or less number. In this manner, therefore, after we have cleared up the internal substance by the application of acetic acid, we again obtain an appearance which reminds us of the original cellform; and there has been the greater tendency to regard the whole of a primitive fasciculus as having sprung from a single cell, because, according to the view which was formerly entertained, the individual primitive fasciculi of every muscle were thought to extend from the point of origin to that of insertion, and were therefore held to be as long as the muscle itself. This latter supposition has, however, been shaken by investigations which were set on foot in Vienna, under Briicke's direction, by Rollet, for he demonstrated that in the course of muscles the ends of primitive fasciculi, are to be seen running into points, so that a primitive muscular fasciculus would comport itself like a large fibrecell (Fig. 105, J). These ends fit one into the other, and, according to this, the length of a primitive fasciculus would by no means correspond to the whole extent of the muscle. On the other hand, I must remark, that observations have been made in different quarters quite recently, which are rather of a nature to throw doubts upon the uni-cellular nature of these elements. Leydig regards them as rather containing a series of cells of a smaller kind, between which the contractile substance is lodged, his idea being based upon the circumstance that every nucleus (Figs. 23,6,c; M, B) is enclosed in a special elongated cavity.1 In
1 This cavity Leyden supposes to be lined by a membrane, and therefore really to constitute a cell (connective-tissue corpuscle). The nuclei of every primitive fasciculus would, therefore, according to this view, be the nuclei of connective-tissue corpuscles, and the contractile substance, lying between these, would be equivalent to the intercellular substance of ordinary connective tissue. The nuclei here alluded to are the ordinary nuclei of muscle, as seen in the figs. quoted above and must not, be confounded with the awl-shaped bodies represented in fig. M, C, lying between the fibrils; for, though these bodies look like nuclei, they are really, according to Leydig, portions of the divided processes of some of his connective-tissue corpuscles.—From a MS. note by the Author.
discussions respecting these ultimate elements of muscle, extremely difficult relations are involved, and I for my own part must confess that, however much I am inclined to admit the uni-cellular nature of the primitive fasciculi, I am still too familiar with the peculiar appearances in their interior not to be obliged to allow that another view may be advanced. For
the present, however, we must bear in mind that we have to do with a structure in which an external membranous sheath (sarcolemma) and contents
are to be distinguished. In the latter, acetic acid causes nuclei to shew themselves, and, when they (the contents) are in their natural condition, the peculiar transverse and longitudinal striation may be recognised in them. This striation is altogether internal, and not external. The membrane in itself is perfectly smooth and even; the transverse striation belongs to the contents, which, when seen in a mass, form the red substance of the muscle.
Now it is this substance which has the property of contractility indubitably inherent in it, and even varies in appearance according to its state of contraction, becoming broader
Fig. 24. Muscular elements from the heart of a puerperal woman. A. Peculiar spindle-shaped cells precisely like the fihrc-cells of the pulp of the spleen, probably belonging to the sarcolemma aud set free in teasing out the preparation, a. Crescentically curved cell, somewhat flat at one end, viewed on its surface, b. A similar one, seen in profile, with flat nucleus, c, d. Cells, the nuclei of which lie in a hernial protrusion of the membrane, e. A similar cell, viewed on its surface, with its nucleus, as it were, lying upon it. B. A primitive fasciculus, without its sheath (sarcolemma), with distinct longitudinal fibrils and large, roundish nuclei, of which one contains two nucleoli (incipient partition). C. A primitive fasciculus, which has been teased asunder and slightly cleared up by acetic acid; besides a divided nucleus, fine, awlshaped, nucleus-like bodies are seen imbedded between the longitudinal fibrils. 300 diameters.