Rabbits 850 and 592 were inoculated intravenously with 0.25 c. c. of a suspension of aspergillus spores and died in ten and thirteen days, respectively. Both of these animals showed pseudotubercles in the lungs, liver, and kidneys, and in No. 850 the suprarenal bodies were involved. (Sce Pl. X, fig. 1.) The lesions in the kidneys were quite characteristic, the nodules in the cortical portion standing out prominently on the surface of the kidneys as distinctly defined tumors or tubercles from 1 to 3 mm. in diameter and of a yellowish white color. Cultures of the aspergillus were recovered from these animals.

This species of animal was also used in testing the action of the filtered product of the Aspergillus fumigatus. These experiments with the toxin of this fungus produced by growing for ten days on Raulin's fluid confirm the work of Obici and others in that the inoculation of the filtrate caused only a transient indisposition and slight increase of temperature.

EXPERIMENTS WITH GUINEA PIGS.

Ten guinea pigs were inoculated with the spores of the aspergillus by various methods.

Three guinea pigs were inoculated each with 0.3 c. c. of a suspension of spores directly into the thoracic cavity and died on the tenth, fourteenth, and seventeenth days, respectively. The postmortem examination showed aspergillar pneumonia, with several tubercles on the pleura. In the first instance a hemorrhagic fringe of fibrous tissue was present on the parietal pleura of the injected side. The diaphragm in each case likewise contained one or more nodules. The livers were sprinkled with diminutive necrotic foci throughout their parenchyma. The kidneys and spleens were normal. Cultures of the fungus were obtained from the liver and lungs.

Three guinea pigs were injected subcutaneously in the left thigh each with 0.5 c. c. of a spore suspension. Two of the animals became lame in the injected leg, but otherwise remained healthy, and when chloroformed twenty-five days later the only alteration observed was about the seat of inoculation. At this point a greenish colored caseous mass was the center of tissue necrosis, involving the surrounding muscular tissue, from which the fungus was recovered on potato media. The third guinea pig was also chloroformed at the same time, but no lesions were found which would indicate aspergillus infection. The two guinea pigs that were inoculated with 0.5 c. c. of a similar suspension intraabdominally remained healthy and when chloroformed, twenty-nine days after their injection, revealed a perfectly normal condition. Culture media inoculated from the various tissues of these animals did not become fertile. The remaining guinea pigs in this series were injected with 0.3 c. c. of the spore suspension intratracheally. Death followed in one case on the third day, with lesions of caseous pneumonia, from which the aspergillus was readily recovered.

The other animal failed to show any ill effects from a similar injection and was perfectly healthy when chloroformed, twenty-five days after its exposure.

DIAGNOSIS.

To diagnose this affection in birds during life is scarcely possible, unless some of the lesions are located in the mouth or upper respiratory passages. On postmortem examination the alterations may resemble tuberculosis or an affection known as acariasis, caused by the animal parasite (Symplectoptes cysticola). A differential diagnosis can readily be made by a microscopic examination of the contents of the nodule and the demonstration of the mycelial filaments. When the bronchial mucosa is affected with mycosis it is very easy to find these filaments and possibly the fruitheads. If the affection is confined to the lung tissues it would be advisable to crush one of the nodules, inoculate a sterilized potato, and incubate twenty-four to forty-eight hours, when it will be possible not only to diagnose the affection, but to say which variety of aspergillus one is handling.

PREVENTION.

In an outbreak of aspergillosis in chickens or other birds the only hope is in prevention, and this will consist in the destruction of the spores about the premises or in discarding contaminated grain or other foods. The buildings and yards should be cleaned thoroughly and the buildings disinfected by the liberal use of fungicides in the form of washes of whitewash to which has been added 5 per cent carbolic acid. The yards may be sprinkled with freshly burned quicklime or chloride. of lime. The drinking and feeding dishes should be kept thoroughly cleaned. Affected birds should be separated from the flock, and all dying from the affection should be buried or burned.

TREATMENT.

Medicinal treatment is probably of little efficacy. If a large number of birds are affected at one time, or if those affected are very valuable, treatment may be tried in the form of medicated vapors, such as those generated from wood tar or sulphur. A small quantity of wood tar is put in a pint of water and stirred with a red-hot iron. The person doing the fumigating should remain in the room and immediately remove any birds that are overcome by the vapors. Burning sulphur or vapors of formalin may be tried in like manner. Hydrogen peroxide, solutions of potassium iodide, or hyposulphite of soda may be used as intratracheal injections, and in case of local nodules in the mouth or nostril the tincture of iodine may be applied to them with beneficial results.

INVISIBLE MICROORGANISMS.

By M. DORSET, M. D.,

Assistant Chief of Biochemic Division, Bureau of Animal Industry.

A REVIEW OF THE SITUATION.

Fifty years ago the nature of infectious diseases was just beginning to be understood. The then existent beliefs concerning the origin of infectious diseases rested almost entirely upon a theoretical basis, and it was not until the beginning of the era of experimental medicine, in which movement Pasteur was the great leader, that any headway was made in the solution of those problems which were finally so brilliantly worked out by Pasteur and his collaborators of that period. The existence of bacteria and other microscopic forms of life had been recognized for more than a century when, in 1850, Pollender and Davaine made their observations upon anthrax, their work being the first experimental evidence of the fact that certain forms of bacteria occupied a causal relation to particular infectious diseases.

During the period between 1850 and 1875 the controversy regarding the spontaneous generation of microorganisms was the all-absorbing topic among biologists, and although this debate did not include the etiology of infectious diseases it involved questions, such as the cause of fermentation, which were so closely allied that the methods employed in the study of the one were in great part applicable to the other.

Thus it was that the foundations of our present-day bacteriological technique were laid, and when, in 1881, Koch gave to the workers in bacteriology his solid-culture media and his "plate method," the principles of sterilization and the methods of staining were already well understood. It is no wonder, therefore, that the decade following Koch's announcement of the "plate method" of isolating bacteria in pure culture was notable for the great advances made in experimental medicine, and especially in that branch of it which concerns the etiology of infectious diseases.

Notwithstanding the many notable advances in that period, however, the causative agents of a certain number of human and animal diseases. completely escaped discovery. New and supposedly favorable culture media were prepared; microscopes were improved in every detail of construction; new staining methods were devised; and, in fact, everything was done which might aid in determining the infectious agents in such diseases as measles, scarlatina, smallpox, rabies, bovine pleuro