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PERINEURIUM AND NEUROGLIA. 279

bellum and cerebrum, between the granules which I have already (p. 269) described to you as connected with large ganglion-cells, and the nuclei of the connective tissue. Whenever the parts are seen severed from their connections, it is not easy to make the distinction, and a positive decision is only possible as long as the parts are viewed in their natural position.

Now it is ccrtainlyof considerable importance to know that in all nervous parts, in addition to the real nervous elements, a second tissue exists, which is allied to the large group of formations, which pervade the whole body, and with which we have in the previous lectures become acquainted under the name of connective tissues. In considering the pathological or physiological conditions of the brain or spinal marrow, the first point is always to determine how far the tissue which is affected, attacked or irritated, is nervous in its nature, or merely an interstitial substance. We thus obtain at the very outset the important criterion for the interpretation of morbid processes, that the affections of the brain and spinal marrow may sometimes be rather interstitial, at others rather parenchymatous, and experience shows us that this very interstitial tissue of the brain and spinal marrow is one of the most frequent seats of morbid change, as for example, of fatty degeneration.

Within the neuro-glia run the vessels, which are therefore nearly everywhere separated from the nervous substance by a slender intervening layer, and are not in immediate contact with it. The neuro-glia extends in the peculiarly soft form, which it presents in the great nervous centres and particularly in the brain, only to those parts which must be regarded as direct prolongations of the cerebral substance, namely to the higher nerves of sense. The olfactory and auditory nerves also contain interstitial substance of the same character, whilst in all the rest, and even in the optic nerve itself, an increasing mass of a tougher tissue; displays itself, which assumes quite the character of perineurium.

Perineurium and neuro-glia are therefore equivalent parts, the only difference being that the one is of a soft, medullary, fragile nature, whilst the other is akin to the well-known fibrous tissues. The neurilemma stands in the same relation to the perineurium that the membranes of the brain and spinal cord do to the neuro-glia.

Wherever neuro-glia exists, a very singular peculiarity presents itself which it has as yet been impossible to explain either chemically or physically, namely, that in every such case those peculiar bodies may be met with, which even in their structure remind one of granules of vegetable starch, whilst in their chemical reactions they altogether correspond to them—the much discussed corpora amylacea (Fig.. 94, ca). They are found to the greatest extent and in the greatest numbers in the ependyma of the ventricles and spinal canal, and are the more abundant the greater the thickness of ependyma. In many places but very few of them are found, whilst in others again their numbers increase so greatly, that the whole thickness of the ependyma is filled with them to such a degree, that it looks as if a pavement were before one. They display themselves however, strangely enough, in pathological conditions also, frequently in great numbers, when, in consequence of some disturbing cause, the quantity of neuro-glia becomes increased in proportion to that of nervous substance, as for example after atrophic processes. In tabes dorsalis, as one used to say, or the atrophy of single columns of the cord, as we now usually interpret the old expression, we find, in proportion as the atrophy progresses, and the nerves in certain directions perish,—cuneiform segments, in which the substance up to that time white becomes from without inwards grey and translucent—there being apparently a production of grey matter. This de

CORPORA AMYLACEA. 281

generation is most frequent in the posterior columns, generally in the immediate vicinity of the posterior fissure, and here it may go on, and generally does go on, in such a manner that the wedge penetrates deeper and deeper and at the same time increases in width. In these parts then the whole substance of the medullated fibres gradually disappears, and distinct nerves are no longer discoverable—

[graphic]

the whole spot generally consisting of neuro-glia with an enormous accumulation of corpora amylacea.

Nowhere in the body has there as yet been found anything completely analogous to structures of this sort, excepting, as I have said, in those parts which appear to be direct protrusions of the cerebral substance, namely in the higher organs of sense, in the case of which originally a certain quantity of central nervous matter entered into the sensorial capsules (Sinneskapseln) of the embryo. In the cochlea too, and the retina, bodies occur, which are allied to the corpora amylacea, although the chemical tests have as yet only proved successful in the case of those found in the internal ear.

When these bodies are isolated, they exhibit in every respect such a complete analogy to vegetable starch that, long before I succeeded in discovering the analogy in

Fig. 96. Section of the spinal marrow in partial (lobular), grey or gelatinous atrophy (degeneration). /. Posterior longitudinal fissure, «, * posterior, w, m anterior nerve-roots, communicating with the grey substance of the horns. In ia slighter, in B a more marked degree of atrophy, which is shewn in the posterior columns around the central fissure/ and in the lateral columns at /. Natural size.

chemical reaction, Purkinjc had already introduced the term corpora amylacea on account of the morphological resemblance. You are no doubt aware, that the chemical correspondence has in many quarters been doubted; the late Heinrich Meckel especially had great doubts upon the subject, and supposed them to have a greater affinity to cholesterine. In more recent times however the matter has been investigated even by professed botanists, and every one who has bestowed close attention upon it, has as yet acquired the same conviction which I published as my own. Nageli pronounces these bodies to be really and truly starch. Morphologically, they present themselves either as perfectly circular bodies with regular, concentric layers, or their centre is a little on one side; or we find twin-bodies; or again the bodies are more homogeneous, pale, with a dim lustre, like fatty substances. When they are cautiously treated with a dilute solution of iodine, they assume a pale bluish, or greyish blue colour, though a great deal certainly depends upon the proper degree of concentration of the test. If afterwards we very cautiously add sulphuric acid, we obtain, when the proper effect is produced, a beautiful blue, which is best shewn by allowing the reagent to act very slowly. When sulphuric acid acts violently upon them, a violet tint, which speedily becomes brownish red or blackish, is obtained, presenting a most decided contrast to the neighbouring parts, which become yellow or at most yellowish brown.

LECTURE XIV.

APRIL 7, 1858.

ACTIVITY AND IRRITABILITY OF CELLULAR ELEMENTS. DIFFERENT FORMS OF IRRITATION.

Life of individual parts. — The unity of the ncurists. — Consciousness.— Activity of individual parts. — Excitability (irritability) as a general criterion of life.—Meaning of irritation.—Partial death.—Necrosis.

Function, nutrition, and formation, as general forms of vital activity.—Difference of irritability according to the different forms of activity.

Functional irritability.—Nerves, muscles, ciliated epithelium, glands.—Fatigue and functional restitution.—Stimuli.—Their specific relations.—Muscular irritability.

Nutritive irritability. — Maintenance and destruction of elements.—Inflammation.—Cloudy swelling.—Kidney (morbus Brightii) and cartilage.— Neuro-pathological doctrines.—Skin, cornea. — The humoro-pathological doctrines. — Parenchymatous exudation, and parenchymatous inflammation.

Formative irritation.—Multiplication of nucleoli and nuclei by division.— Multi-nuclear cells; medullary cells and myeloid tumours.—Comparison between formative muscular irritation and muscular growth.—Multiplication (new-formation) of cells by division.—The humoro- and neuropathological doctrines.

Inflammatory irritation as a compound phenomenon.—Neuro-paralytical inflammation (Vagus, Trigeminus).

I Have given you, gentlemen, a somewhat lengthy sketch of the histological arrangements of the body, in order to make the inference plain to you, which in my opinion must be the starting point of all future considera

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