Page:Proceedings of the Royal Society of London Vol 2.djvu/62

Rh That the laws which regulate their effects on the muscles of voluntary and involuntary motion are different.

That both mechanical and chemical stimuli applied to any part of the nervous system tend to increase the action of the heart.

That neither mechanical nor chemical stimuli applied excite the muscles of voluntary motion, unless they are applied near the origin of the spinal marrow.

That mechanical stimuli have more effect than chemical on voluntary muscles, but the reverse with respect to those of involuntary motion.

That all stimuli continue to affect the heart long after they have failed to excite the muscles of voluntary motion.

That the motions thus excited in voluntary muscles are irregular, but those of the heart more regular.

That the former occur chiefly at the first moment of application, but those of the latter as long as the stimulus is applied.

That the former depend on intensity of the stimulus, the latter on the extent of surface to which it is applied.

That the power of the blood-vessels, like that of the heart, is independent of the nervous system, though they may be influenced through that system, as the heart is.

That the actions thus excited are regular, as those of the heart, and that their power, like that of the heart, may be destroyed through the nervous system. 



The great sources of fire-damp in coal mines are blowers or fissures from which currents of this inflammable gas issue in considerable quantities and for a long series of years; but there is also a certain quantity produced by the workings. The author was informed by Mr. Hodgson, that if a cask be filled with a quantity of recently pounded coal, and a small aperture be made in it, inflammable gas will issue from the aperture.

In several specimens of fire-damp which the author has analysed, the inflammable part was the same in all; in some instances mixed with a small quantity of common air, in others with azote and carbonic acid. The purest contained only th of atmospheric air. One measure of this gas required nearly two measures of oxygen for its combustion, and formed nearly one measure of carbonic acid. Sulphur heated in this gas decomposed it, forming sulphuretted hydrogen, and precipitating charcoal.

This gas, when mixed with chlorine, does not combine by exposure to light; so that it appears to contain neither olefiant gas nor hydrogen, and seems to be the same as the inflammable gas of marshes, or pure carburetted hydrogen.