lungs may be slightly congested, but otherwise not changes are to be found.

When the various organs, which present no appreciable changes to the naked eye, are subjected to a microscopic examination, the appropriate staining methods bring out a most remarkable and beautiful change. The capillary system is almost universally occupied by bacilli, which extend throughout its meshworks in long threads. Most beautiful bundles of these bacillary threads can, at times, be found in the glomeruli of the kidney and in the minute capillaries of the intestinal villi. In the larger vessels, where the blood-stream is rapid, the bacteria are relatively few, so that the burden of bacillary obstruction is borne by the minute vessels. The condition is thus seen to be one of pure septicemia, and bacilli can be secured in pure cultures from the blood and tissues.

The susceptibility of the anthrax bacillus to the influence of heat, cold, antiseptics, etc. not only permitted Buchner, Behring, and others to produce biological curiosities in the form of bacilli unable to bear spores and robbed of their pathogenic powers, but also suggested to Pasteur the important practical measure of protective vaccination. Pasteur found that the inoculation of nonvirulent bacilli into cows and sheep, and their reinoculation with slightly virulent bacilli, gave them the ability to withstand the action of highly virulent organisms. Löffler, Koch, and Gaffky, however, found that these immunized animals were not absolutely protected from intestinal anthrax.

The methods of diminishing the virulence of the anthrax bacilli are numerous. Toussaint, who was certainly the first to produce immunity in animals by injecting them with sterile cultures of the bacillus, found that the addition of 1 per cent. of carbolic acid to blood of animals dead of anthrax destroyed the virulence of the bacilli; Chamberland and Roux found it removed when 0.1-0.2 per cent. of bichromate of potassium was added to

the culture-medium; Chauveau used atmospheric pressure to the extent of six to eight atmospheres and found the virulence diminished; Arloing found that direct sunlight operated similarly; Lubarsch found that the inoculation. of the bacilli into immune animals, such as the frog, and their subsequent recovery from its blood, diminishes the virulence markedly.

Protection can be afforded in still other ways. The simultaneous inoculation of bacteria not at all related to anthrax will sometimes recover the animal, as Hüppe found. Hankin found in the cultures chemical substances, especially an albuminose, which exerted a protective influence. Chamberland has shown that protective inoculation by Pasteur's method has diminished the death-rate from 10 per cent. for sheep and 5 per cent. for cattle to about 0.94 per cent. for sheep and 0.34 per cent. for cattle, so that the utility of the method is scarcely questionable. In 1890, Agata and Jasuhara showed that in the convalescents from anthrax among their experimental animals an antitoxic substance was present in the blood in such quantities that 1: 800 parts per body-weight of dog's serum containing the antitoxin would protect a mouse. Similar results have been attained by Marchoux.

Experiments of interest have been performed to show that the natural immunity enjoyed by many animals can be destroyed. Behring found that if the alkalinity of the blood of rats was diminished, they could become affected with anthrax, and numerous observers have shown that when anthrax bacilli and unrelated organisms, such as the erysipelas cocci, Bacillus prodigiosus, and Bacillus pyocyaneus, are simultaneously introduced into immune animals, the immunity is destroyed and the animals succumb to the disease. Frogs have been made to succumb to the disease by exposure to a temperature of 37° C. after inoculation. Pasteur destroyed the immunity of fowls by a cold bath after inoculation.

In the natural order of events anthrax in cattle is

probably the result of the inhalation or ingestion of the spores of the bacilli from the pasture. At one time much discussion arose concerning the infection of the pasture. It was argued that, the bacilli being enclosed in the tissues of the diseased animals, the infection of the pasture must be due to the distribution of the germs from the buried cadaver to all parts of the field, either through the activity of earth-worms, which ate of the earth surrounding the corpse and then deposited the spores in their excrement at remote areas (Pasteur), or to currents of moisture in the soil. Koch seems, however, to have demonstrated the fallacy of the theories by showing that the conditions under which the bacilli find themselves in buried cadavers are exactly opposed to those favorable to fructification or sporulation, and that in all probability the majority of bacteria suffer the same fate as the animal cells, and disintegrate, especially if the animal be buried at a depth of two or three meters.

Fränkel points out particularly that no infection of the soil by the dead animal could be worse than the pollution of its surface by the bloody stools and urine, rich in bacilli, discharged upon it by the animal before death, and that in all probability it is the live, and not the dead, animals that are to be blamed as sources of infection.

As every animal affected with anthrax is a source of danger to the community in which it lives, to the men who handle it as well as the animals who browse beside it, such animals, as soon as the diagnosis is made, should be killed, and, together with the hair and skin, be burned. When this is impracticable, Fränkel recommends that they be buried to a depth of at least 11⁄2-2 meters, so that the sporulation of the bacilli is impossible. The dejecta should also be carefully disinfected with 5 per cent. carbolic-acid solution.

Of course, animals can be infected through wounds. This mode of infection is, however, more among men, who suffer from the local disease manifested as the malignant carbuncle, than among animals.

CHAPTER X.

TYPHUS MURIUM.

THE Bacillus typhi murium (Fig. 113), which created havoc among the mice in his laboratory, causing most of them to die, was discovered by Löffler in 1889. It is a short organism, somewhat resembling the bacillus of chicken-cholera. It is rather variable in its dimensions, and often grows into long, flexible filaments.

No

sporulation has been observed. It is a motile organism, with numerous flagella, like those of the typhoid-fever bacillus. It stains well with the ordinary dyes, but rather better with Löffler's alkaline methylene blue.

Upon gelatin plates the deep colonies are at first round, slightly granular, transparent, and grayish. Later they become yellowish-brown and granular. Superficial colonies are similar to those of the typhoid bacillus. In

gelatin punctures there is no liquefaction. The growth takes place upon the surface principally, where a grayishwhite mass slowly forms.

Upon agar-agar a grayish-white development devoid of peculiarities occurs.

Upon potato a rather thin whitish growth may be observed after a few days.

The bacillus grows well in milk, with the production. of an acid reaction, but without coagulation.

The organism is pathogenic for mice of all kinds, which succumb in from one to two days when inoculated subcutaneously, and in eight to ten or twelve days when fed upon material containing the bacillus. The bacilli multiply rapidly in the blood- and lymph-channels, and cause death from a general septicemia.

Löffler expressed the opinion that this bacillus might be of use in ridding infested premises of mice, and the results of its use for this purpose have been highly satisfactory. He has succeeded in ridding a field so infested as to be useless for agricultural purposes by saturating some bread with bouillon cultures of the bacillus and distributing it near the holes inhabited by the mice. The bacilli that were eaten by the mice not only killed them, but also infected others which ate the dead bodies of the first victims, and so the extermination progressed until scarcely a mouse remained in the field. The bacilli are not pathogenic for the animals, such as the fox, weasel, ferret, etc., that feed upon the mice, do not affect man in any way, and so seem to occupy a useful place in agriculture by destroying the little but almost invincible enemies of the grain.