cessfully stained the bacterium tuberculosis in tuberculous expectorations, and in numerous thin sections made from different tuberculous lungs, and, while still testing different methods of staining, I observed in sections, stained with methyl violet, and decolored by alcohol, that, though no stained bacteria could be discovered in the section, a number of nuclei had retained some of the blue color, while the rest of these bodies had given it up. At the same time, I noticed in the interior of these nuclei several granular bodies of a slightly deeper stain. Regarding these stained nuclei as having been formed more recently than those unstained, and the bodies which they contained as their ordinary, legitimate granules, I attached no particular importance to this observation. Some time afterward, however, when again examining sections, made from the lungs of a case of typical miliary tuberculosis, and stained by Gibbes' method, first with magenta and then with chrysoidine, I observed the same phenomenon, though more distinctly than before. In these sections, in which the tubercles were comparatively small, and in which no bacteria tuberculosis whatever could be discovered in their cheesy degenerated centres, I observed a number of deeply stained granules, as well as granular filaments, in the interior of the nuclei of the tubercle-cells occupying the periphery of the tubercle. Whilst these bodies, which in every respect resembled bacteria, were deeply stained by the purplish blue of the magenta, the protoplasm of the nucleus itself was stained yellow by the chrysoidine. This observation explained to me at once not only the cause of the peculiar grouping of the bacteria tuberculosis, as observed in the cheesy parts of the tubercles, but,

moreover, their true origin in the nuclei of the tubercle-cells, and also showed me the direction in which my investigations had to be further pursued. In examining other sections of the same lung, stained in the same manner, I then observed the same purplish blue bodies not only in the interior of the nuclei of the tubercle-cells, but also in the nuclei of all the cells contained in the different tissues of the bronchioles adjacent to tubercles; that is, in the nuclei of the connective tissue-cells of the mucous and fibrous coats (fig. 6 a) in those of the muscular fibre-cells (fig. 6 b) and even in those of the cartilage-cells contained in the minute cartilaginous plates of the bronchioles. I furthermore observed these bodies in the nuclei of the cells of the adventitia of some of the smaller arteries. By repeatedly observing this same phenomenon afterward in sections made from the tuberculous lungs of other cases, especially of miliary tuberculosis, I was, at last, convinced of the bacterial nature of these stained bodies within the nuclei of the bronchial walls; the more so as they were not observed in the nuclei of the walls of bronchioles. not adjacent to tubercles, nor in those of the healthy parenchyma of the lungs. While these bodies were stained of a deep purple by the magenta, the protoplasm of the nuclei appeared stained more feebly by the same color, indicating that the latter were affected by some irritation, probably derived from the neighboring tubercle. In staining these sections with a second color, such as chrysoidine or Bismarck brown, it was absorbed by the protoplasm of the nuclei, while the bacteria within the latter kept their purple tint; only when exposed a comparatively long time to these second colors, the bacteria assumed a brownish tint, though much darker that that of the nuclear protoplasm.

The correctness of the observations just described, I found corroborated by the examination and study of a very considerable number of stained sections, taken not only from the lungs of cases of miliary, but also of chronic tuberculosis, and of tuberculous livers, spleens and lymphatic glands, in which the same well-stained granular bodies were always observed in the interior of the nuclei of those tubercle cells occupying the periphery of the tubercle. All that now remained to prove the bacterial nature of these bodies was to meet with such sections of tuberculous tissue in which not only the origin and development of the bacteria tuberculosis in or from the protoplasm of the nuclei, but also their liberation from the latter could be clearly demonstrated. By the close examination of numerous well stained sections of large miliary tubercles of the lungs, liver and spleen, or of such tubercles situated near the borders of the tuberculous portions of the lungs of cases of chronic tuberculosis, I succeeded, at last, in tracing in one and the same section the bacterium tuberculosis from its first appearance in the nuclei of the tubercle cells to its full development and its liberation from the degenerated nuclei in the cheesy centers of the tubercles. Specimens of tubercles in which the bacterium tuberculosis can be traced from its origin to its liberation are, for certain reasons, to be stated directly, not found in every tuberculous portion of lung, liver, etc., though they are often enough met with, especially if properly looked for, to furnish to every investigator ample opportunity to corroborate the correctness of my statements.

As far as I know from the current medical literature it has now been asserted by a number of investigators on the subject under discussion, that free bacteria tuberculosis cannot be discovered in all tubercles, and, moreover, that whenever

they are met with in tuberculous tissues, it is principally in that portion of tubercle, or tuberculous mass, in which the process of coagulation-necrosis is going on. My own observations not only corroborate the truth of the statements of these authors, but also enable me to furnish in the following pages the explanation for this phenomenon.

From my observations it appears that the development of the bacteria tuberculosis in the nuclei of the tubercle cells stands in a certain relationship with the degree or rapidity of the degenerative process taking place in the nuclei; in other words, the more rapid the course of the degenerative process, -not only of the nuclei but also of the protoplasm of the cells, the smaller is the chance for the bacteria to reach their full development or maturity; whilst on the other hand, the more slowly this process proceeds, the more time will be afforded to these organisms for reaching their full development and their final liberation from the degenerated protoplasm of the nuclei.

The appearance of the bacteria in the nuclei is always preceded by a shriveling of the nuclear protoplasm, indicating that the degenerative process has commenced. The normally round outlines of the nucleus, then, become irregular, whilst its double contour appears darker and more prominent. With the advancing degeneration the irregularity of the outlines of the nucleus increases, whilst its margin, represented by the double contour, is breaking up, first into a few and then into more fragments, which are finally converted into a number of minute filaments of a granular or bead-like composition. In the course of the degenerative process the power of retaining aniline colors against decolorizing agents, such as nitric or formic acid, etc., increases in the margin of the nucleus, and in the fractions into

which it has broken up, in proportion to the degree of degeneration. It is thus that in thin sections of tuberculous tissue, stained with magenta, the irregular shriveled margins appear of a dark red, which ultimately, in the filamentous fragments changes into purple.

Whilst the above described changes are observed to take place in the protoplasm of the nuclei, that of the cells, of course, undergoes the same degeneration. Accordingly the bodies of the cells appear paler and paler, until finally their outlines can be no longer distinguished, their protoplasm having lost all power of absorbing coloring materials, and undergone the coagulation-necrosis. As far as I am able to judge, the degenerative process not only commences in the protoplasm of the cells, but runs there a more rapid course than in that of the nuclei. This is seen in examining the cheesy centres of miliary tubercles, in which no trace of the outlines of the cells can be discovered, while a number of shriveled nuclei, containing forms of more or less perfectly developed bacteria, or minute fragments of nuclei, are still met with. Judging, however, from the fact observed in these cases, that the remains of the protoplasm of these nuclei still present the yellow color of the chrysoidine, or Bismarck brown with which the section was lastly stained, whilst the bacteria show the purple of the magenta, it appears to me that the protoplasm of the nuclei never undergoes a perfect degeneration, as, otherwise, it would not have retained its capacity of absorbing coloring matters. It seems, therefore, more probable that the shriveling of the nucleus stands in some relation to the development of the bacteria, for the more fully the latter are developed, the more the nucleus shrivels; in other words, the protoplasm of the nucleus ap