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PACINIAN BODIES.

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able distance up, whilst in the human body they are situated only at the root of the mesentery, where the duodenum comes in contact with the pancreas in the neighbourhood of the solar plexus. Moreover they present great variations in different individuals. Some have very few, others a great number, of them, and it is very possible that certain individual peculiarities result therefrom. Thus I have, for example, on several occasions found a great number of these bodies in lunatics, though I do not wish at present to lay any great stress upon this discovery.

A Pacinian body, as seen with the naked eye, is of a whitish colour, usually oval and somewhat pointed at one end, from a line to a line and a half (1—1 J'") long, and firmly attached to a nerve in such a way that a single primitive fibre passes into each body. It presents a comparatively large number of elliptical and concentrical layers, which at the upper end are in pretty close contact, but at the other are separated by a wider interval, and enclose in their interior an oblong space, generally somewhat more pointed towards the upper end. Within these layers nuclei can be distinctly seen disposed in regular order, and on following the layers towards the stem of the

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Fig. 82. Vaterian or Pacinian body from the subcutaneous adipose tissue of the end of a finger. S. The peduncle, consisting of a dark-bordered, medullated primitive nerve-fibre », and the thick perineurium p, p provided with longitudinal nuclei. C. The body itself with the concentric layers of the perineurium which is swollen out into a bulbous shape—and the central cavity, within which the pale axis-cylinder is seen running along and terminating in a free extremity. 150 diameters.

nerve, they are there observed finally to pass into the perineurium which is in this part very thick. They may therefore be regarded as gigantic developments of the perineurium, which however only enclose a single nerve-fibre. Now on tracing the nerve-fibre itself we observe that its medullated portion usually extends only up to the beginning of the body, when the medulla disappears and the axis-cylinder is seen continuing its course alone. It then runs on through the central cavity, and terminates at no great distance from the upper end generally simply, yet often in a little bulbous swelling,1 and in the mesentery very frequently in a spiral coil. In rare cases it happens that the nerve divides and several branches pass into the body. But in every case we seem to have before us a mode of termination. What these bodies signify, what office they perform, whether they have anything to do with the function of sensation, or whether their province is to develop any one of the properties of the nervous centres, we are as yet entirely ignorant.

A certain degree of resemblance to these structures is exhibited by the tactile bodies which have been recently so much the subject of discussion. When the skin and more especially the sensitive part of it is microscopically examined, two sorts of papillae, as was first discovered by Meissner and Rud. Wagner, are distinguished, the one narrower, the other broader, though certainly intermediate forms are met with (Fig. 83). In the narrow ones we constantly find a simple, in broader ones of the same class— a branching, vascular loop, but no nerve. This point is so far of importance, that we have, by means of these observations, been made acquainted with a new nerveless structure. In the other kind of papillae we very frequently find no vessels at all, but on the other hand nerves, and those peculiar structures which have been designated tactile bodies.

1 Quite recently Jacubowitsch has, as he thinks, discovered a gauglion-cell in this part.—MS. Note of Author.

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A tactile body manifests itself as an oblong-oval structure, tolerably distinctly marked off from the remainder of the papilla, and has, with some degree of boldness indeed, been compared by Wagner to a fir-cone. It is generally rounded off at the upper and lower end, and does not exhibit a longitudinal striation, as the Pacinian bodies do, but on the contrary transverse nuclei. Now a nerve runs up to every one of these bodies, and from every one of them a nerve returns, or more correctly, we usually see two nervous filaments, generally pretty close to one another, which can be readily traced up to the side or base of the body. After this point their course is very doubtful, and in different cases the conditions vary so much that we have not yet succeeded in making out with certainty the relation of the nerves to these bodies. In many

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Fig. 83. Nervous and vascular papilla? from the skin of the end of a finger, after the separation of the epidermis and rete Malpighii. A. Nervous papilla with a tactile body, up to which ascend two primitive nerve-fibres n; at the base of the papilla fine clastic networks e, from which fine fibres radiate, between and on which connective-tissuc-corpusclcs arc to be seen. B, C, D. Vascular papillae, with, at C, simple, at li and D, branching vascular loops, and in addition fine elastic fibres and connective-tissue-corpuscles; p, the papillary body running its horizontal course, at c fine stellate cells belonging to the cutis proper. 300 diameters.

cases namely the nerve is very distinctly seen to ascend and also to entwine itself around the body. Sometimes it seems as if the body really lay in a nervous loop, and thus the possibility of a more concentrated action on the part of external agencies upon the surface of the nerve was provided for. At other times again it looks as if the nerve came to a termination much sooner, and buried itself in the body. Some have assumed, with Meissncr, that the body itself belongs to the nerve which resolves itself into it. This I do not hold to be correct, and the only point which seems to me to be doubtful is, whether the nerve ends in the body or forms a loop around it.

Apart from anatomical and physiological considerations, this example is of great value in the interpretation of pathological phenomena, because we here find two complete contrasts in parts which in themselves are quite analogous; for, on the one hand, we have nerveless but vascular, on the other, non-vascular, papillae, yet provided with nerves. The peculiar relations which the layers of the rete mucosum and epidermis bear to the two kinds of papillar, do not appear to present any essential differences. They are nourished just as perfectly over the one sort as over the other, and seem to be just as little provided with nerves over the one as over the other.

These are facts which indicate a certain independence in individual parts and furnish distinct evidence that parts of considerable size and even richly provided with nerves can subsist, maintain their existence and perform their functions without vessels, and that on the other hand parts which relatively contain numerous vessels, can absolutely dispense with nerves without incurring any disturbance in the state of their nutrition.

LECTURE XII.

MARCH 31, 1858.
THE NERVOUS SYSTEM.

Peripheral terminations of the nerves.—Nerves of special sense.—The skin and the distinction of vessel-, nerve- and cell-territories in it.—Olfactory mucous membrane.—Retina.—Division of nerve-fibres.—The electrical organ of fishes.—Muscles.—Further consideration of nerve-territories.— Nervous plexuses with ganglioniform enlargements.—Intestines.—Errors of the neuro-pathologists.

The great nervous centres.—Grey substance.—Ganglion- [nerve-] cells containing pigment.—Varieties of ganglion-cells; sympathetic cells in the spinal marrow and brain, motor and sensitive cells. Multipolar (polyclonous) ganglion-cells.—Different nature of the processes of ganglion-cells.

I Return, gentlemen, to-day once more to the skin. The difference which exists between the individual papillae of the skin seems to me so important theoretically, that I think I must claim your special attention to it. In the greater number of the papillae we see, as I mentioned to you the last time, a single or, when the papilla is very large, a branched, vascular loop. The majority of these vascular papillae have no nerves; others again which contain tactile bodies, no vessels. If we imagine the vessels and tactile bodies removed, there remains only a very small quantity of substance in the papilla, but within it there still are morphological elements, and it is easy to convince oneself that connective tissue with its corpuscles (which latter after injection are very easily distinguished from the vessels), is

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