in other respects it is rather variable; the fluid is often almost clear, with a slight orange sediment, which rises up in columns upon shaking. At other times there is a slight transitory cloudiness. In sugar bouillon the growths are identical.

Milk culture exactly like Mycob. lacticola.

Potato Culture.-Like that of the glycerin-agar streak. Indol is produced only as a trace, HS not at all, and also no gas is liberated. Acid production is the same as by Mycob. lacticola. Gelatin is not liquefied.

Pathogenic Effects of Mycobacterium lacticola and phlei.1

According to the descriptions of all authors, the pathogenic action of these varieties is so similar that it is not worth while to treat them separately.

It is ageed that the organisms are essentially less pathogenic without the simultaneous injection of butter, and even that the resulting peritonitis (adhesions, membranous formations, fibrinous and purulent exudates) may be dependent upon the injection of butter alone (Hormann and Morgenroth); still, the intraperitoneal injection of large quantities of pure cultures often produces an infection and causes the formation of nodules in the abdominal organs, yet the process often heals. If animals are killed three or four weeks after the injection of large quantities, the following conditions are found (Rabinowitsch): Slightly distended abdomen, more or less severe peritonitis, the peritoneum and mesentery beset with nodules, numerous small nodules beneath the intestinal serosa, mesenteric glands perceptibly swollen and often caseated. Likewise the liver, spleen, and kidneys show yellowish exudation in nodules in variable degrees. The lungs exhibit, at most, numerous transparent nodules, and are usually free from more serious disease. The transfer of small pieces of the organs to a new animal transfers the disease, according to Rabino

1 Animal experiments appear to have been performed by Rabinowitsch, Hormann, and Morgenroth exclusively, and by Petri in part, with Myc. lacticola. Petri and Moeller have worked with Myc. phlei. Also Korn's experiments with his Myc. friburgense correspond except in unessential matters.

witsch; but according to Petri, and Hormann and Morgenroth, this only occurs if tuberculosis is simultaneously present.

When butter is experimented with (4 to 5 c. c. of the previously thoroughly mixed mass, melted at 37° and containing butter-fat, watery part, and casein layers), if the bacilli are present in abundance, a fatal result often follows the injection after three to fifteen days. There are then found changes similar to those described above, only very much more intense, the abdominal organs being covered with well-developed inflammatory, fibrinous membranes which are swarming with the organisms.

Rabinowitsch found rabbits insusceptible in contrast to guinea-pigs. It is generally admitted that guinea-pigs are the most suitable experimental animals, although single reports concerning infection of rabbits are not lacking.

Korn could infect only mice with the pure culture of his Friburgensis (0.5 c.c. of a suspension or larger doses). Whether injected into the blood-vessels, subdurally, or into the kidneys, the organisms produce more or less well-developed areas, such as described on page 416 in true tuberculosis: i. e., formations resembling actinomycosis, but which disappear in the course of months. The animal body destroys the organisms which are introduced (Lubarsch and O. Schultze).

Also, in the structure of the accompanying miliary tubercles, these authors can often detect no difference from those of true tuberculosis.

Little has yet been learned concerning the distribution of the organisms resembling the Mycobac. tuberculosis. However, it appears very wide, for about 60% of butter samples in Berlin contained such organisms, and the investigations of Moëller demonstrated their frequent occurrence in manure, on grasses, etc. Lubarsch and Dieu

donné verified this.

To obtain the acid-proof bacteria from butter, about 4 gm. are injected intraperitoneally in two guinea-pigs with a wide cannula, as indicated above. After about six to ten days the animals, if not dead, are killed, and cultures are prepared from the contents of the abdominal cavity which yield acid-proof bacteria, growing at room temperature.

To tirate the organisms from grass, the grass is covered with water Phleum pratense is especially recommended and allowed to remain at 37° for thirteen to twenty-four hours. When frequent (every two hours) examinations have demonstrated that acid-proof organisms are present in quantity, plates are prepared.

It cannot be stated with certainty whether these new varieties of mycobacteria may also be pathogenic for man. So far as we know, no acid-proof organisms which grow upon all nutrient media and at room temperature have been cultivated from the sputum in cases of pulmonary diseases or from human organs.

Ginsberg stained numerous bacteria from two cases of eye disease, which were closely related to the T. B., but they were not cultivated (C. B. xxii, 62).

Flexner described a Streptothrix pseudotuberculosa Fl. from the lung of an old negro, growing with beautiful branching, staining by Gram's method, but imperfectly acid-proof with the T. B. stain, and not certainly pathogenic for guinea-pigs (Jour. of Exp. Med., m, 435).

Differential Diagnosis of the Mycobact. tuberculosis (Tubercle Bacillus; T. B.).

1. If the T. B. is to be distinguished from bacteria which are not acid-proof, simple preparations are stained by the Ziehl-Neelsen method. Those which do not stain can be left out of question. T. B. which do not stain by the Ziehl-Neelsen method are unknown.

In the examination of sputum one proceeds as follows: The sputum is to be obtained as free as possible from foods and secretions from the mouth, and it is best collected in a sterile dish after the mouth has been well washed with water. Of the sputum, the more purulent (not mucous) portions, which are in lumps, are selected, spread upon the cover-glass, and stained (see Technical Appendix).

If no bacilli are found in a few preparations, although tuberculosis is suspected of being present, then one of the more searching methods described in the Technical Appendix must be employed in the attempt to discover isolated. bacteria.

2. For the differentiation of T. B. from lepra and smegma bacilli the present methods scarcely suffice. T. B. are difficult to cultivate; lepra and smegma organisms are only very rarely cultivated successfully. For the tinctorial differences, see pages 422 and 425.

3. There is no difficulty in differentiating the T. B. from "pseudotubercle bacilli" which grow well at room temperature, so long as only one variety is present. Agar or gelatin plates are prepared and kept at 22°. True tubercle bacilli do not grow at all, at least when they come from warm-blooded animals, while the false varieties grow out well in two to four days. Reinoculations are made upon glycerin-agar and into bouillon in order to differentiate Myc. phlei and Myc. lacticola.

We are unable to suggest a method for recognizing culturally the true T. B. when associated with large numbers of bacilli resembling it; in cultures the true T. B. would be overgrown. According to the present state of our knowledge, a guinea-pig must be injected intraperitoneally with a moderate amount of the mixture.

If the guinea-pig dies after the intraperitoneal injection of small amounts of culture (one loopful) and without the addition of butter, with well-marked tuberculous changes in the abdominal cavity (enlargement of liver and spleen), and with involvement of the respiratory organs, these speak in favor of true tuberculosis. The histologic examination must give a predominance of true, giant-celled tubercles; and from the nodes and nodules organisms must be cultivated which will not grow at room temperature and on ordinary nutrient media, but at incubator temperature and upon ascites-glycerin-agar in the case of true T. B. Since death from tuberculosis in guinea-pigs usually occurs six weeks after the infection, before that the few germs resembling the T. B. are absorbed and have disappeared.

4. To determine whether a person or an animal is tuberculous, the injection of tuberculin is often made use of. Although it does not lack in individual contradictory results, yet there is no doubt that the tuberculin reaction constitutes a very important aid.

It is customary to inject cows subcutaneously with 0.3 to 0.5 c.c. of tuberculin, and to observe whether an eleva

tion of temperature of 1.5° to 2° or 2.5° occurs after twelve to fifteen hours. A French commission speaks especially favorably of it (C. B. XIX, 645). The reaction sometimes is absent when the animal is extensively diseased, but for these cases the reaction is not required. It scarcely ever appears in healthy animals, and here it is to be remembered that small areas are often to be found with difficulty at the postmortem. The result is not influenced by other diseases in cattle. Exceedingly rarely, latent tuberculosis is stimulated to new activity. It is of importance that an animal often fails to give a positive reaction a second time for a month after a typical reaction was first obtained.

The question does not appear to have been investigated as to whether the tuberculin reaction occurs in animals infected with Mycob. lacticola and Mycob. phlei.

Naturally it is much more difficult to come to a conclusion regarding the reliability of the tuberculin reaction in man, since it cannot be controlled subsequently by thorough postmortem examinations; at any rate the injection of tuberculin in man for diagnostic purposes is not employed to any great extent.

3. Actinomyces. Harz, emend. Gasperini.

Growths upon solid nutrient media are elevated, tough, more or less wrinkled, often cartilaginous. Microscopically, they appear as long, thin, elongated mycelial threads, the young ones with homogeneous contents without partition walls, without a developed covering, and with abundant, true branches. In older threads there can be distinctly recognized a delicate membrane, and within it the colored contents, broken up into fragments. Positive cell divisions are rarely observed in cultures of varieties of actinomyces. Some varieties, in the animal body, present clubbed enlargements upon the ends of the radially arranged threads, which are to be explained as thickenings of the sheath (see below). Many species form chains of short colorless spores (conidia) upon thickened air hyphæ (two to ten times thicker than the threads) which rise above the solid medium and compact culture film like a