Page:Popular Science Monthly Volume 19.djvu/146

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136
THE POPULAR SCIENCE MONTHLY.

them; on the other hand, housed vegetable-feeding animals—stags, antelopes, oxen, sheep, and goats—if reared by hand from birth, become when adult the most dangerous animals to be met with; while, if caught after they have grown up, they are timid and fly from man. His experience with all animals of the latter class has been the same as with the lamb, whose case he describes, that was brought up as "one of the family." As it grew larger and stronger, it became self-conscious and independent, having "no fear and less gratitude," and grew so saucy that it had to be consigned to a large field, where it became a terror to passers—for, "with hop, skip, and jump, he was behind any one in an instant; with one good spring, the unfortunate traveler was on his hands and knees if not on his face "—and was finally sentenced to the butcher. Such of these animals as have been bred in captivity (not petted and handled) and reared by the parent, become exceedingly wild if an attempt is made to catch them, pack them up, or move them from one place to another. The reason for these curious manifestations appears to be that the tamed animals, having lost their fear of man and become familiar with him, when the time comes for them to manifest their belligerent propensities, have no respect of persons, and are ready to attack their former friend as they would any other real or imaginary antagonist; but, when anything new is attempted with them, it is as novel as it would be in their natural state, and awakens all their natural wildness.

 

Fungi as Insecticides.—The possibility of putting a limit to the depredations of noxious insects by cultivating the fungi which are destructive to them has been several times suggested. Professor Le Conte recommended the study of the epidemic diseases of insects, particularly of the fungoid diseases, with this view, in 1874. Charles II. Peck, State Botanist of New York, advanced a similar idea with reference to the fungi which infest plants, in 1876, and in 1878 described a large destruction of seventeen year-locusts and of the larvæ of insects feeding upon the alder by fungi. Dr. H. A. Hagen, of Harvard University, in 1879, thinking he had established the identity of the fungus which destroys the house-fly with the yeast fungus, recommended the use of the latter against noxious insects in general. Professor A. N. Prentiss, of the Botanical Laboratory, instituted a series of experiments during the spring of 1880 with the plants in the laboratory, upon the effects of the yeast-fungus upon the aphides and other insects preying upon them. The record of his experiments is given in the form of a journal in contributions to "The American Naturalist." The result of nine experiments as a whole, as also of many others not recorded, indicates that yeast can not be regarded as a reliable remedy against such insects as commonly affect plants cultivated in greenhouses and dwellings. The attempt to use it is liable to the further objection, that it will be very likely to injure many kinds of plants quite as badly as it will the insects. The experiments of Mr. Trelease, of Selma, Alabama, with the yeast upon the cotton-worm, led him to a similar conclusion with reference to its application to that insect. On the other hand, according to Dr. Hagen, Mr. J. H. Burns, of Shelter Island, New York, has had some success with yeast against the Colorado potato beetle, and it has been used upon the aphides in a greenhouse in Germany with great success. Professor Prentiss does not consider the question at issue decided by his experiments, for the yeast-fungus may be operative on other insects and under other conditions than those with which he performed his experiments, and there may be other forms of fungus which, applied with discrimination, would be effective.

 

Examination of Germs in the Air.—Dr. Ferdinand Cohn and Dr. Miflet, of Breslau, have been investigating experimentally as to the possibility of detecting the organisms which are regarded as the germs of infection and fermentation in the air in which they are supposed to float. Their experiments were carried on from the middle of March to the end of July, 1878, in the air of laboratories, operating-rooms, and the sick-rooms of hospitals; in the free air of the botanical gardens, and the air gathered at the surface of the soil of the garden; and in the sewer-air of a court. They found—1. That numerous germs exist in the air in