Page:Popular Science Monthly Volume 53.djvu/443

Rh than 500 writers; and about 700 entomological papers have appeared since then from the agricultural experiment stations. Hence, the author estimates the bulk of writings on insects available now at between 12,000 and 15,000 volumes; and this does not include the recent literature of apiculture. On a similar basis of calculation it is estimated that there are between twelve and fifteen hundred people now living whose works on insects are of such a character as to be noticed in the standard annual books of record. Besides these are the writers on bees, and the very large number of collectors of insects who rarely write on the subject. The number of species of described insects, excluding arachnids and myriapods, is estimated at 250,000; and it may be that, the world over, there are 10,000,000 species in all. Thus only one in forty of probably existing species is known—a fact that seems to throw grave doubt on much of our classification and characterization of genera. About 1,200 new genera and subgenera are added every year. "That the entomologists of the world have ample material with which to work, and that there is no alarming prospect in the immediate future of exhaustion of the field, is strikingly apparent." Dr. David Sharp has recently computed that in the matter of bulk insects probably outrank all other animals together, their small size being more than counterbalanced by the vast number of species and enormous multitude of individuals.

Economical Uses of Bacteria.—Prof. H. Marshall Ward, in his presidential address, which was read in his absence before the Botanical Section of the British Association, dwelt at considerable length on the many industrial processes which depend more or less for their success on bacterial fermentations. The subject is young, he says, but the little that has been discovered makes it imperative that we should go on, for the results are of immense importance to science, and open up vistas of practical application which are already taken advantage of in commerce. A bacillus has been discovered by Alvarez which converts a sterilized decoction of indigo plant into indigo sugar and indigo white, the latter then oxidizing to form the valuable blue dye, whereas the sterile decoction itself, even in the presence of oxygen, forms no indigo. Certain stages in the preparation of tobacco leaves and of tea depend on a carefully regulated fermentation, which must be stopped at the right moment, or the product is impaired or even ruined. While in flax and hemp the best fibers are separated by steeping in water till the middle lamella is destroyed, not every water is suitable for the process, but only that containing a particular bacillus, which destroys the pectin compounds of the lamella and leaves the cellulose. A process depending on this fact has been patented in the United States. The steeping of skins in water preparatory to tanning involves bacterial action for removal of the hair and epidermal coverings; and the swelling of the limed skins is a fermentation process. Hay and ensilage have to go through fermentations involving bacterial action. The various flavors of butter and cheese are each produced by special bacteria, and the cultivation of them has become a considerable business, so that the production of whatever flavor may be desired has become a matter of reasonable certainty.

Areca and its Properties.—The areca nut, a favorite stimulant of the many millions of people living in the East Indies and beyond, is the fruit of a tree, the Areca catechu, which, as described by M. Ernest Martin, following Chinese authors, has a trunk like that of the bamboo, straight and without branches, jointed in the upper part, with leaves like those of millet or sugar cane, under which are spathes containing fruits about as large as plums and protected by thorns. These nuts are edible. The bark of the tree is like that of the Paulownia; and it is on the whole very like the cocoa palm. It is regarded as one of the handsomest ornaments of the woods of the southern part of the extreme East. The nut is extensively used as a stimulant and as a remedy. It forms the basis of a preparation, with betel and lime, which is made to be chewed. After it has been used for a little while the teeth begin to assume a dark yellow or even blackish hue, from which the Chinese say that the Cochin-Chinese, Annamites, Cambodians, etc., tattoo their teeth. The effect sought in chewing areca is an excitation which, affecting the