854 



THE POPULAR SCIENCE MONTHLY, 



dom. The insects were placed in strong 

 alcohol for some days, and the isolated fibers 

 of the legs or trunk were examined with va- 

 rious powers. Each fiber or primitive fas- 

 ciculus 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 ap- 

 parently sometimes obscurely segmented into 

 portions surrounding each nucleus. The 

 nerve-endings, or terminal plaques, as M. 

 Toettinger calls them, are situated on the sur- 

 face of the fiber, and their free surface is cov- 

 ered with a thin, structureless, transparent 

 membrane, continuous with the sarcolernma 

 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 ex- 

 clusively. 



An Improved Smokeless Grate. Dr. C. 



.W. Siemens has recently proposed to rem- 

 edy 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 constitu- 

 ents is possible, and a smokeless and clean- 

 ly 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 perfo- 

 rated 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 incandes- 



cent 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 thi'ough 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 thou- 

 sand 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. Experi- 

 ment has shown that, to heat a large room, 

 eight feet of gas burned in this grate arc 

 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 pres- 

 ent gas plant, as gas companies produce 

 both the gas and the coke in about the pro- 

 portions used, and this Dr. Siemens regards 

 as an additional point in their favor. 



Elevator Pnennionia. 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 na- 

 tionality subject to affections of the lungs, 

 work in gangs, shoveling in a close atmos- 

 pljere 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 



