small degree to be ascribed to the increased pressure to which the venous blood is subjected.

What I was particularly anxious, gentlemen, to render evident to you, was the great difference which this kind of fatty degeneration presents from that which we have previously considered. Whilst there we saw arise between the proper specific constituents of the organ-fat-cells which belonged to the connective tissue, here it is the specific glandcells themselves which are the seat of the fat. On the other hand, you must take into consideration the great difference from the necrobiotic processes of fatty degeneration, in which the cells as such disappear.

We have now, gentlemen, to consider this third series of fatty conditions a little more closely, those, I mean, which are attended by a destruction of the elements, and of which we have set up the secretion of milk and sebaceous matter as the true types. That these two secretions are analogous to one another, is simply explained by the circumstance that the mammary gland is really nothing more than an enormously developed and peculiarly formed accumulation of cutaneous (sebaceous) glands. In their development both classes are perfectly analogous. Both are produced, by means of a progressive proliferation, from the internal layers of the epidermis (p. 40, Fig. 18, 4). To the same category also belong the ceruminous glands of the ear, and the large glands of the axilla. In all these cases the fat, which constitutes the chief constituent of milk, at least as far as its external appearance is concerned, and which furnishes the sebaceous secretion, originates in the interior of epithelial cells which gradually perish and set the fat free, whilst scarcely a trace of the cells is preserved. The sebaceous glands are generally seated on the sides of the hair-follicles at some depth below the surface; we there find a series of minute lobules, into which a prolongation of the rete mucosum is uninterruptedly continued.

FORMATION OF SEBACEOUS MATTER AND MILK. 335

FIG. 111.

The cells of this become more numerous and larger, so as to fill the gland-sacs with a nearly solid matter. Then the fat begins to be secreted into their interior, at first in small particles, which soon become larger, and after a short time the individual cells can no longer be distinctly perceived, but only conglomerations of large drops, which rise up out of the gland into the hair-follicle. If we unravel the gland so as to form a flat surface, its layers of cells would have the g appearance of epidermis, only that the oldest cells do not become horny, but are destroyed by fatty metamorphosis. The secretion is a purely epithelial one, like the seminal secretion.

This process furnishes us at the same time with an accurate representation of the formation of milk. You need only imagine the ducts much lengthened, and the terminal acini greatly developed; the process remains essentially the same: the cells multiply abundantly; the multiplied cells undergo fatty degeneration, and ultimately there remain scarcely any material traces of these cells excepting the drops of fat. The closest resemblance to the manner in which the secretion of sebaceous matter ordinarily takes place, is presented by the earliest period of lactation when the so-called colostrum is yielded. A colostrum-corpuscle

Fig. 111. Hair-follicle with sebaceous glands from the skin. c. The hair, bits bulb, e, e, the layers of cells dipping down from the epidermis into the hair-follicle. gg. Sebaceous glands in the act of secreting sebaceous matter; at f, the secretion mounting up by the side of the hair and accumulating. 280 diameters.

(Fig. 112, C) is the still coherent globule which results from the fatty degeneration of an epithelial cell. The formation

of colostrum and sebaceous matter differs in this respect only, that the fat-granules remain smaller in the former case, and that whilst large drops very soon shew themselves in sebaceous matter, in colostrum the last cells which are observed, usually contain only minute fatgranules, very densely aggregated, whereby the whole cell acquires a somewhat brownish appearance, although the fat has no actual colour. This is the granular corpuscle (corps granuleux) of Donné.

For the discovery of this gradual transformation of cellular bodies into fat-granule masses we are indebted to Reinhardt. Still he shrank from extending this important discovery of the formation of colostrum to the history of milk in general, for the reason, that, during the later periods of lactation properly so-called, granulated bodies are no longer met with. It is, however, unquestionable, that between the earlier formation of colostrum-corpuscles and the later one of milk, there is no other difference than this, that in the formation of colostrum the process goes on more slowly, and that the cells maintain their cohesion

Fig. 112. Mammary gland during lactation, and milk. 4. Lobule of the mammary gland, with milk issuing out of it. B. Milk globules. C. Colostrum, a, a distinct fat-granule cell, b, the same with evanescent nucleus. 280 diameters.

COLOSTRUM- & MILK-CORPUSCLES. GRANULE-CELLS. 337

longer, whilst in the secretion of milk the process is acute and the cells more speedily perish. Perfectly developed colostrum contains an extremely large number of granulated corpuscles, milk nothing more than a number of comparatively large and small drops of fat, mixed up together, the so-called milk-corpuscles (Fig. 112, B), which are nothing more than drops of fat, and like the majority of the drops of fat that occur in the animal body are surrounded by a delicate, albuminous membrane, called by Ascherson the haptogenic1 membrane (Haptogenmembran). But the individual drops (milk-corpuscles) correspond to the drops which we find in the secretion of sebaceous matter; they are produced by the coalescence of the minute granules which appear in the secretion of colostrum.

Now that we have seen these types of physiological transformation, gentlemen, the description of the pathological changes no longer offers any difficulty. With the exception of very few structures, as for example, red bloodcorpuscles and the nerve-fibres in the great nervous centres, nearly all other cellular parts may under certain circumstances undergo a similar metamorphosis, which displays itself in a precisely similar manner, that is, isolated, extremely minute globules of fat appear in the cell-contents, become more abundant, and gradually fill up the cell-cavity without, however, running together into such large drops, as is the case in fatty infiltration and in the adipose-tissue formations. Usually, the development of the fat-granules first declares itself at some distance from the nucleus; very seldom does it begin at the nucleus. This is the cell which has long been called the granule-cell. Then comes a stage, in which the nucleus and membrane are indeed still to be seen, but the fat-granules lie as close to one another as in colostrum corpuscles; only at the spot

i.e., produced by contact.-TRANSL.

where the nucleus lay, there is still a little gap (Fig. 66, 6). From this stage there is but a short step to the complete destruction of the cell. For a cell never remains for any length of time in the state of a granule-cell, but as soon as it has once entered into this stage, the nucleus generally disappears at once, and ultimately the membrane also, probably by a species of solution. Then we have the simple granule-globule, or as it was formerly called, inflammatory globule [exudation-corpuscle], which Gluge first described under this name (Fig. 66, c).

Gluge in this made one of those mistakes which not unfrequently marked the early periods of microscopy. He saw, when examining a kidney, bodies of this sort in the interior of a canal, which he took for a blood-vessel; this happening at a time when the doctrine of stasis was most in vogue, he imagined he had before him a vessel with stagnating contents which were disintegrating, and generating inflammatory globules. Unfortunately the blood-vessel was a uriniferous tubule; what he took to be parts of disintegrating blood-corpuscles, was fat; and what he called inflammatory globules, fattily degenerated renal epithelium. One might easily have spared oneself this error in the history of stasis, but at that time there were few people who knew what was the appearance of uriniferous tubules and how they might be distinguished from vessels, and thus some time elapsed before this theory of inflammation was put down.

At present we call the body a granule-globule and regard it as the first distinct proof of degeneration, when the cell no longer retains its existence as a cell, but merely its former shape remains, after the parts which really constitute a cell, namely the membrane and the nucleus, have completely passed away. After this, in accordance with external circumstances, either a complete destruction of the parts ensues, or they may still persist, coherent. If,