place, gradually adapt itself to the new conditions, and even, in the course of successive transformations, acquire new facilities for adaptation. If four vessels, carefully cleansed, are tilled with different fluids—such as carbolic acid, urine, Cohn's mineral plant-food, and Pasteur's fluid—all clear of bacteria, and a drop of the same putrefactive mixture is added to each of them, they will, in the course of forty-eight hours, show very different degrees of disturbance, according to their adaptation to promote the growth of the infective organisms. If the organisms themselves are examined, they will be found, although all originating from the same source, to be only similar, not identical. Even Pasteur, who stoutly advocates the specificity of the ferments, has been obliged to admit a few exceptions to his theory. Dr. Wernich had already called attention to observations by himself and others which tended to show that fungoids, which seemed harmless growths on the more exposed tissues, might, if the capacity of the body for resistance should be depreciated, become aggressive, and develop dangerous disorders. Grawitz cultivated a mold that grows on sour solids, but does not flourish in the bodies of animals, through successive generations, till he adapted it to a higher temperature than its natural one, to pastes, sweetened and alkaline fluids, and to blood. A living animal inoculated with spores of the last variety died in a few hours in consequence of a general development of the fungoid vegetation, particularly in the kidneys and liver. Dr. Wernich believes that he has evidence that the strength of the infective qualities of these organisms may be greatly increased by an accommodative culture. Cultivation in substances unfavorable to their growth is, on the other hand, found to cause a depreciation of their inoculative efficacy. If we select the most favorable substance for the growth of a mold, and plant upon it the most vigorous stocks we can obtain, we will soon perceive unmistakable indications of an increase of vigor. The period required for the development of the germs is shortened, and the organisms give way to their successors of the next generation in continually diminishing periods. The infective force becomes so much greater that the slightest contact is sufficient to effect a transplantation to a new medium, and the greatest pains are necessary to prevent a transfer without apparent contact of spores of the same kind as those which, subjected to unfavorable conditions of culture, require painful attention to induce them to take root in any new soil. A similar development of activity and infective power may be observed in the case of epidemics. The germs of disease do not exhibit their full vitality at once, as do poisons when absorbed, but require a period of incubation and the favor of diminished power of resistance in the body before they can exhibit their full effect. The first cases are indefinite, and hardly recognizable in their real character, and affect only the weakly; as the epidemic acquires strength, its manifestations are mere determinate, and it affects all. The manner in which this growth of activity is produced may be illustrated by experiments that have been made in the inoculation of animals, in which an increase in infective power has been very distinctly perceived to accompany each successive transfer from one animal to another. Dr. Wernich suggests that there are some questions relating to the subject that need yet to be explained, and that it will not be safe to form definite conclusions upon it until after further investigation.
Explosive Force of Coal-Dust.—The Rev. H. C. Hovey has communicated to the "American Journal of Science" the results of the investigations of Mr. Gilpin, Inspector of Mines for Nova Scotia, into the part played by coal-dust in spreading and augmenting the explosions which took place in the Albion mine in November of last year. The mine was thoroughly ventilated, and was reported by the night-watchman, an hour before the explosions began, to be free from gas, except in small and harmless quantities. Yet the explosions, once begun, were continued at intervals till the mine was all aflame and had to be flooded. On examining the gallery shortly after the original explosion, dead bodies of men and horses were found six hundred yards from the shafts, and the wood-work was splintered, but nothing bore any marks of fire, "and the conclusion was plainly justifiable that