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Page:Popular Science Monthly Volume 18.djvu/874

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dom. The insects were placed in strong alcohol for some days, and the isolated fibers of the legs or trunk were examined with various powers. Each fiber or primitive fasciculus presents several nerve-endings, which are attached to the muscular fiber apparently without any definite rule as to their position or distribution. The muscular elements to which they are fixed are usually conical in form, a nerve running to the summit of each cone. The cone itself is composed of granular matter, with nuclei interspersed through it; and the granular matter is apparently sometimes obscurely segmented into portions surrounding each nucleus. The nerve-endings, or terminal plaques, as M. Foettinger calls them, are situated on the surface of the fiber, and their free surface is covered with a thin, structureless, transparent membrane, continuous with the sarcolemma of the muscular fiber on the one hand and the sheath of Schwann investing the nerve fiber on the other. In insects contraction always begins in the muscular fiber at the plane' of the cones, and at those points exclusively.


An Improved Smokeless Grate.—Dr. C. W. Siemens has recently proposed to remedy the smoke-nuisance, where it is due to the burning of bituminous coal in private houses, in a very simple way. Instead of burning such fuel in its crude state, in which the volatile and solid constituents are combined, he makes use of them after they have been industrially separated into the forms of coal-gas and coke. In these forms perfect combustion of both constituents is possible, and a smokeless and cleanly fire is produced at but little greater cost than with coal, and considerably less than gas alone. In order to burn the gas and coke together. Dr. Siemens has devised a simple and inexpensive modification of the ordinary grate, that can readily be made in any existing one. The construction consists in covering the bottom bars of a grate with a metal plate, which is bent to extend up the back, and in placing a gas-pip along the lower front edge. This pipe is perforated on its upper side, the holes being a little inside of the middle line, so that the gas-flames incline slightly inward. The grate is filled with coke, which becomes incandescent upon its surface from the flame passing over it, and, as the interior of the mass is not heated, the maximum radiation from a given amount of fuel consumed is obtained. The coke has, of course, to be from time to time replenished, and the ashes removed, but in neither of these operations is there the trouble, or the dust and dirt, incident to the ordinary method of burning coal. Air is allowed to enter only in front, so that the mass of coke is protected from cooling drafts by the layer of hot gases. The heat of the bottom bars of the grate may be made to warm the air supplied to the gas, by a bent plate placed below, so as to form a chamber through which this air has to pass. Compared with the various forms of gas grate. Dr. Siemens estimates that the cost for. fuel is largely in favor of this. A thousand cubic feet of ordinary illuminating gas develops by its combustion 748,000 heat units, and costs in London eighty-seven cents, while, to produce the same amount of heat by coke, fifty-six pounds are requisite, the cost of which is but eleven cents. Experiment has shown that, to heat a large room, eight feet of gas burned in this grate are sufficient, while fifty to seventy feet. Dr. Siemens states, are needed in a grate using gas only. Such grates could go into use very largely without any change in the present gas plant, as gas companies produce both the gas and the coke in about the proportions used, and this Dr. Siemens regards as an additional point in their favor.


Elevator Pneumonia.—The pulmonary diseases to which men employed in elevators are subject are described in an article by Dr. Thomas F. Rochester, published in the "Buffalo Medical and Surgical Journal." These men, who are generally Irish, of a nationality subject to affections of the lungs, work in gangs, shoveling in a close atmosphere which is teeming with dirt and dust and bearded particles of grain, often for thirty-six hours—sometimes, they assert (although the employers deny it), for six or seven days and nights at a time. They are liable to contract a disease which is known in the hospitals as elevator pneumonia. A new man, soon after he begins to work in the elevator, experiences catarrhal, nasal, and throat irritation; and, while he may