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the same subject. He coincided with Dr. Burnett in his observation of facts, but wished the investigation extended to include the region of the Wolffian bodies. He had satisfied himself that these bodies originated in the capillary system of the pellucid area of the embryo. There is a circulation within the transparent area of the embryo long before any circu. lation of blood takes place ; — a circulation of a transparent fluid containing no blood corpuscles, but consisting of a series of cell nuclei in a transparent fluid. From the resolution of a series of these nuclei the circulation originates, and it is entirely confined to the region of the head, in which the heart is formed. He believed that there were three layers of the blastoderma as first represented by C. E. von Baer, and that these layers are essentially distinct.

As soon as the eighteenth hour after incubation, the basis from which the Wolffian bodies grow may be detected; he believed that these facts had hitherto been entirely overlooked. The terminations of the Wolffian bodies are combined into a vesicle, from which vesicle the allantois is properly a bud.

With reference to the physical deductions of Dr. Burnett, he had one objection to make. Naturalists were too apt to describe the functions of the organs of undeveloped animals by phraseology derived from the functions of animals in a more advanced condition. He believed this to be dangerous, and, notwithstanding the analogy between the allantois and a urinary bladder, as shown by Dr. Burnett, he could not coincide in the inference.

Dr. Burnett said that his views of the Wolffian bodies were quite different from those of Mr. Agassiz, and that he intended to present them, at an early meeting, to the Academy.

Professor Peirce described an experiment upon the forms assumed, and the motions which arose, in a globule of oil held in suspension in an alcoholic solution.

Professor Agassiz called attention to the analogy between these forms and motions, and those which arise in the earliest embryonic cells.

Threo hundred and sixty-ninth meeting.

October 12, 1852. — Monthly Meeting. The President in the chair.

The President, in behalf of the committee appointed to provide for the delivery of the Academy's course of lectures, reported that the requisite arrangements had been completed. The course was given as follows, commencing on Wednesday evening, October 27th, at half past seven o'clock, and continued on successive Wednesday evenings:

By Jacob Bigelow, M. D., President, Introductory Lecture. By Professor L. Agassiz, Genealogy of the Animal Kingdom.

By Professor C. C. Felton, Relation of Aristophanes to his Times.

By George Ticknor, Esq., The Tartuffe of Molière.
By Dr. B. A. Gould, Jr., The Theory of Probability.

By Daniel Treadwell, Esq., The Progress of the Useful Arts, and their Relation to Scientific Discovery.

By President Edward Hitchcock, The Bird Traces of Connecticut River.

By Lieutenant Charles H. Davis, Astronomical Prediction. By Professor C. C. Felton, Aristophanes, Second Lecture. By Professor Albert Hopkins, Time.

By Oliver Wendell Holmes, M. D., The Relations of Poetry and Science.

By George B. Emerson, Esq., A Higher Course of Instruction in Science in Reference to Preparation for exercising the Useful Arts.

By Hon. Samuel A. Eliot, A Complete System of Public Education.

Mr. Horsford exhibited to the Academy specimens of his newly invented safety-lamp and safety-can, and described the precautions which had been taken to guard against accidents.

Dr. W. I. Burnett read a paper upon Cartilaginous and Osseous Tissues.

“ The cartilaginous tissue, wherever found, is invariably the same. VOL. III.

Two varieties, however, dependent upon degree of organization, are met with :

“ The first is cellular cartilage, being of a transient nature, ultimately to be changed into bone. It is composed of nucleated, welldefined cells lying in a semi-solid, punctiform stroma.

" The second is fibro-cartilage of a permanent nature, and consisting of the same cells as the first, but which lie in a network of fibrous tissue, which last is only a further developed condition of the punctiform stroma.

“In fibro-cartilage the fibrous tissue may so increase at the expense of the cellular elements, that these last almost entirely disappear, and hence the transition of fibro-cartilage into fibrous tissue.

“ From this it will appear that all cartilage is originally the same, that is, cellular, appearing as such in the embryo.

" Its formation there, according to my own observation, occurs in the following manner.

" At those points where cartilage and afterwards bone is to appear, there are seen cells which, as to physical characteristics, cannot be distinguished from those which are to form other tissues.

“A part of these cells are condensed into a punctiform stroma, leaving open spaces here and there, in which the original cells in numbers from one to four remain. Thus is ultimately seen a finely granular stroma, inclosing free nucleated cells. This is the true cellular cartilage.

" As this stroma is formed closely about the cells, it is not correct to say that cavities are formed in it, and in which the cells lie. For the cell-membrane, lying in direct contact with the stroma, blends with it, the nuclei alone, therefore, being left in the cavity ; but as these are nucleolated, they resemble cells, and should be thus designated.

“In fibro-cartilage the same early changes occur, but the stroma is further developed into a fibrous or fibrillated tissue. Where this has occurred, the cell-nuclei lie in nidiform cavities.

“ Cellular cartilage alone is developed into bone. This occurs in the following manner. When the ossific matter is about to be deposited, the vascularity of the cartilage is much increased, having a pinkish hue. Then a kind of liquefaction of the stroma intervening the cells takes place, by which the cartilage-cells appear no longer confined irregularly, but are, for the most part, free to assume any relative position. Soon after this, there is seen with them a ten

dency to an arrangement in a linear series. The rows thus formed run parallel with the long diameter of the bone, and are separated from each other by the intercellular matrix, which consists of the par. tially liquefied stroma.

" It is thus that the future bone may be said to consist of a fasciculus of tubes filled with cartilage cells. This intercellular matrix constitutes the primitive ossific rete, in which the calcareous salts are first deposited. This first deposition having taken place, the cartilagecells are situated in cup-like, or rather cylinder-like, cavities.

" During this time, however, the cartilage-cells, and the substance immediately surrounding them, are likewise changed from the pres. . ence of calcareous matter.

“ The cells become smaller, and, in contracting, assume irregular forms, and the septa separating the tubes in which they formerly lay become more and more indistinct from the fulness of the cal. careous deposition. Finally, a grayish mass is perceived, having little regularity, and variegated in aspect by the presence of strangely shaped bodies, the future Purkinjean corpuscles. But these processes should be described a little more minutely. During the calcareous deposition, the aqueous portion of the tissue disappears, and, the size of the whole being reduced, the cartilage-cells are brought nearer together; the tissue, therefore, is much more compact, but has not lost its original characteristics. The tubes of which we have spoken form the concentric lamella, in which the corpuscles are regularly arranged ; and thus a transverse section shows them to be solid cylinders instead of hollow tubes as before the calcareous deposition.

The cartilage-cells are transformed into the Purkinjean or os. seous corpuscles. This I have clearly observed, and have traced all the phases of the change. Where the cells are in the cup-like cavities, their nuclei are prominent. But as ossification proceeds they gradually crumble away, and by the time ossific matter is deposited in the cellwalls, little of them can be seen. The cells, however, remain in a shrunken state, holding a concentric relation to a continuous cavity of the tube, and which cavity is the Haversian canal. When the cartilage-cells begin to shrink, radiating lines are seen running from each, and in reaching out in every direction, they meet and join those of contiguous cells, and thus a connection is formed on every side.

“ The question now arises, What are these canaliculi ? Are they, according to Schwann, prolongations of the cartilage-cell membrane ;

or, according to Owen and others, radiations of its nucleus? My own opinion is different from either, and for the following reasons. In the first place, the canaliculi do not begin to form until calcareous matter is deposited, and, as the cell-membrane is then either filled with calcareous matter, or partially absorbed, it could not well send out prolongations. Moreover, these last are often of such a length, and so branch and rebranch upon themselves, that such a mode of formation seems hardly possible. To me it appears most probable that they are the channels of escape of aeriform matters from the interior of the cell. For the cell, situated in the midst of an ossifying mass, would retain for some time its animal matter, and this last would ultimately give rise to gases seeking their escape in every direction by percolating the surrounding semi-solid mass. Canaliculi would thus be formed, and these, converging towards the nearest outlet, have therefore been rightly called “converging tubuli.?

“During these phases of formation, some of the nuclei of the cartilage-cells, or even whole other cells of a small size, may not be dissolved, but become ossified as such. They are then found as celllike corpuscles scattered through the osseous tissue. It is in this way that I account for the occasional presence, in the spongy tissue of the long bones, of small spherical bodies, first discovered in 1849 by Dr. O. W. Holmes of this city.

" Such appear to be the processes of formation of the compact tissue of the bones of the higher Vertebrata, as I have studied them in fætal goats.

“ The whole process is simply one of substitution, with that contraction and modification of form which necessarily ensues when a soft is replaced by a sclerous tissue.

“ This process of substitution is carried out everywhere the same, there being, however, variations in some steps of its progress in the different kinds of bones. The spongy nature of the internal or middle portions of some bones appears to be produced by the absorption, by numerous vessels there situated, of the lighter portion of the primitive cartilaginous base, and a consolidation of the remaining portion towards the periphery.

“ This is a point, however, having an unusual teleological bearing, for by such process bones possess the greatest combined strength and lightness attainable with the same amount of material.

“These phases of formation just described belong especially to the

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