But

arrive at the result which Reinhardt has set down as the final one, namely, that tuberculosis is nothing more than one of the forms presented by inflammatory products when undergoing transformation, and especially that all tuberculous matter is really inspissated pus. In fact, what has been termed tubercular infiltration, can with few exceptions be traced to an originally inflammatory, purulent or catarrhal mass which has gradually, in consequence of incomplete reabsorption, fallen into the shrivelled and shrunken state in which it afterwards remains. Reinhardt was deceived when he thought he was examining tubercle. He was led astray by the false direction which had been given to the whole doctrine of tuberculosis from the time of Laennec until his own, especially through the fault of the Vienna school. If he had confined himself in his investigations to the form of old assigned to tubercle, the knot (granule), if he had examined the constitution of the knot in its different stages and had afterwards compared the different organs in which knotted (granular) tubercle occurs, he would unquestionably have arrived at a different result.

It may, at least according to what I consider to be the correct view of the matter, certainly be said, that the greatest part of whatever in the course of tuberculosis does not appear in the form of granules, is an inspissated inflammatory product, and has at any rate no direct relation to tubercle. But by the side of these inflammatory products, or also independently of them, we find a peculiar structure [the knot, granule] which, if they are to be regarded as real tubercle, would no longer be included in the ordinary classification ; and it is certainly an extremely characteristic circumstance that in France, where the terminology of Lebert has become the prevailing one, and the corpuscules tuberculeux are wont to be regarded as the necessary accompaniments of tuberculosis-bodies, concerning the tuberculous nature of

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which there can be no doubt, have quite recently been set down as something altogether peculiar and which had hitherto remained undescribed. For one of the best, nay perhaps the best, micrographer France possesses, Robin, has, in his examinations of cases of tubercular meningitis, deemed it impossible to regard the little granules in the arachnoid1 [pia mater] which everybody looks upon as tubercles, as being really tubercles, because the dogma now prevails in France that tubercle consists of solid non-cellular corpuscles, and in the tubercles of the cerebral membrane cells in a state of perfect preservation are met with. To such curious aberrations does this track lead that one ends by being unable to find a name for real tubercle, because so many accidental objects have been confounded with it, that what was sought for, or even what had been found and was already grasped, has, in consequence of the attention of observers being diverted by these objects, been allowed to slip out of one's hand again. I am of opinion that a tubercle is a granule, or a knot, and that this knot constitutes a new-formation, and indeed one, which from the time of its earliest development is necessarily of a cellular nature, and generally, just like all other new-formations, has its origin in connective tissue, and which, when it has reached a certain degree of development constitutes a minute

The so-called visceral (cerebral) layer of the arachnoid is only the superficial layer of the pia mater which is spread evenly over, and does not dip in between, the convolutions, and being (as the name, arachnoid, implies), of a reticulated texture contains spaces (subarachnoid spaces). The so-called parietal layer of the arachnoid is only the inner superficial layer of the dura mater with the epithelium lining it. The Author employs the term arachnoid in general only for the purpose of making himself more intelligible to others, but as this superficial layer of the dura mater does not possess a reticulated structure and is everywhere inseparably connected with the rest of the membrane, and as epithelial coverings are not wont to be designated by special names, he of course always uses the term of the pia mater. Such expressions, therefore, as the "sac" or "cavity of the arachnoid" are incorrect.-Based upon MS. notes by the Author.

knot within this tissue, that, when it is at the surface, projects in the form of a little protuberance, and consists throughout its whole mass of small uni- or multi-nuclear cells. What especially characterizes this formation is the circumstance, that it is extremely rich in nuclei, so that when it is examined as it lies imbedded in the tissue which

invests it, at the first glance there seems to be scarcely anything else than nuclei. But upon isolating the constituents of the mass, either very small cells provided with one nucleus are obtained-and these are often so small that the membrane closely invests the nucleus-or larger cells with a manifold division of the nuclei, so that from twelve to twenty-four or thirty are contained in one cell, in which case, however, the nuclei are always small and have a homogeneous and somewhat shining appearance.

This structure which in its development is comparatively most nearly related to pus, inasmuch as it has the smallest nuclei and relatively the smallest cells, is distinguished from all the more highly organized forms of cancer, cancroid and sarcoma, by the circumstance, that these contain large,

Fig. 140. Development of tubercle from connective tissue in the pleura. The whole succession of transitions is seen from the simple connective-tissue corpuscles, the division of the nuclei and cells up to the production of the tubercle-granule, the cells of which in the middle are disintegrating into fatty granular débris. 300 diameters.

SOLITARY TUBERCLES OF THE BRAIN.

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voluminous, nay often gigantic corpuscles with highly developed nuclei and nucleoli. Tubercle, on the contrary, is always a pitiful production, a new-formation from its very outset miserable. From its very commencement it is, like other new-formations, not unfrequently pervaded by vessels, but when it enlarges, its many little cells throng so closely together, that the vessels gradually become completely impervious and only the larger ones, which merely traverse the tubercle, remain intact. Generally fatty degeneration sets in very early in the centre of the knot (granule), where the oldest cells lie (Fig. 140), but usually does not become complete. Then every trace of fluid disappears, the corpuscles begin to shrivel, the centre becomes yellow and opaque, and a yellowish spot is seen in the middle of the grey translucent granule. This is the commencement of the cheesy metamorphosis which subsequently characterizes the tubercle. This change advances from cell to cell farther and farther outwards, and it not unfrequently happens that the whole granule is gradually involved in it.

Now, the reason why I think that the name of tubercle must be specially retained for this formation, as being extremely characteristic of it, is this-that the tuberclegranule never attains any considerable size, and that a tuber never arises out of it. Those which are wont to be termed large tubercles, and attain the size of a walnut, or a Borsdorf apple,' as for example in the brain-those are not simple tubercles. You will generally find the tubercles in the brain described as being solitary, but they are not simple bodies; every such mass (tuber) which is as large as an apple, or even not larger than a walnut, contains many thousands of tubercles; it is quite a nest of them which

1 Borsdorf apples are very constant in their size, and measure from an inch and a half to an inch and three quarters (1"-13") in diameter.-From a MS. nole by the Author.

enlarges, not by the growth of the original focus (granule), but rather by the continual formation and adjunction of new foci (granules) at its circumference. If we examine one of these perfectly yellowish white, dry, cheesy tubera, we find immediately surrounding it a soft, vascular layer which marks it off from the adjoining cerebral substance-a closely investing areola of connective tissue and vessels. In this layer lie the small, young granules, now in greater, now in less, number. They establish themselves externally [to the previously existing ones] and the large tuber grows by the continual apposition of new granules (tubercles), of which every one singly becomes cheesy; the whole mass, therefore, cannot in its entirety be regarded as a simple tubercle. The tubercles themselves remain really minute, or as we are wont to say, miliary. Even when on the pleura, by the side of quite small granules, large yellow plates, looking as if they were deposited upon the surface, are met with, these too are not simple tubercles, but masses composed of a large aggregate of originally separate granules.

Here, you see, form and nature are in reality inseparably connected. The form is produced by the growth of the tubercle from single cells of connective tissue, by the degenerative proliferation of single groups of connective-tissue corpuscles. Thus, without more ado, it appears at once in the shape of a granule. As soon as it has once attained a certain size, as soon as the generations of new corpuscles which develop themselves out of the old histological elements by a continual succession of divisions, at last lie so close to one another, as to cause a mutual arrest of development, gradually to induce the disappearance of the vessels of the tubercle, and thereby to cut off their own supplies, then they begin to break up, they die away and nothing remains behind but débris-shrunken, disintegrated, cheesy material.