SANCTORIUS, CRUIKSHANK, EDWARDS. 133

In whatever light we view it, the skin is, in all animals, a most important organ; and so much so as drolly enough, with the exception of the human subject, to have been long popularly familiar. Yet so imperfect have been the investigation of its functions, that we are at this moment chiefly indebted to the early experiments of Abernethy for what we know that is positive on the subject. The original experiments of Sanctorius were quantitative and, as general truths, of sufficient importance to have excited more attention. Cruikshank's were highly acceptable, but they were less numerous and less varied than those of Abernethy, whilst the labours of Edwards, though exhibiting great industry and zeal, were by no means so conclusive as those of Abernethy. Edwards' experiments served to strengthen and confirm, by the analogy afforded by other animals, conclusions drawn by Abernethy from the more secure premises furnished by the observation of corresponding functions in man.

Mr. Abernethy's inquiry was first directed to ascertain what the skin actually gave off from

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the body; and secondly, what changes took place in the air which we draw into the lungs (inspiration). We will endeavour to give some idea of these experiments. They were very simple they involved no cruelty like those of Edwards-and they were many of them such, as the public might repeat without difficulty.

Very useful would it be if persons who have leisure would sometimes engage in physiological inquiries. They would find them to be extremely interesting, and a series of facts would be easily collected, from which the physiologist might obtain the most valuable information, but which, engaged as most of them are in applying physiology to the correction of disordered functions, they can seldom collect for themselves, except in a few hours stolen from those occupied in an arduous profession, and perhaps by the sacrifice of paramount duties.

Mr. Abernethy's experiments were very numerous, and commenced in the summer of 1791; but the winter's cold obliging him to desist, they were renewed in the spring of

HIS EXPERIMENTS IN QUICKSILVER.

135

1792. Having referred to the experiments of Ingenhous and Cruikshank, together with an allusion to a paper (not then made public) by Lavoisier, he proceeds to describe his own.

Having a trough containing a large quantity of quicksilver, he filled a glass jar (sufficiently capacious to contain his hand and wrist) with that metal. He inverted it into the trough in the usual way of proceeding in collecting gases. He fixed the glass jar in a sloping position, that he might introduce his hand the more readily beneath the quicksilver. In this way, whatever was given off from the skin of the hand, rising through the quicksilver to the top of the glass, and of course displacing a proportionate quantity of quicksilver, could be made the subject of analysis.

He describes his first experiment as follows: "I held my hand ten minutes in the "jar beneath the surface of the quicksilver, " and frequently moved it in that situation, in "order to detach any atmospheric air that

might accidentally adhere to it, and afterwards

"introduced it into the inverted jar. The quicksilver soon acquired a degree of warmth

136. EXPERIMENTS IN QUICKSILVER.

"which rendered it not unpleasant. Minute "air-bubbles ascended to the top of the quick

silver, more speedily in the beginning of the "experiment, more tardily towards the con"clusion. After an hour had elapsed, I with"drew my hand; the bubbles of air, which now appeared on the top of the quicksilver, were, I

suppose, in bulk equal to one scruple of water.

"In sixteen hours, I collected a half-ounce "measure of air, which makes fifteen grains

the averaged product of an hour. No kind "of moisture appeared on the surface of the quicksilver. Some sucking-paper was put 66 up, which was withdrawn unmoistened. My "hand was always damp when taken out of the

66

quicksilver. Whatever aqueous perspiration "was produced adhered to its surface, whilst "the æriform ascended to the top of the jar. "To the air I had 'thus collected, I threw "up lime-water, when about two-thirds of "it were rapidly absorbed; to the remainder "I added a bubble of nitrous gas;t but

*The test for carbonic acid.

† A test for the presence of oxygen.

EXPERIMENTS IN WATER.

137

"could not discover any red fumes, nor any "diminution of the quantity. I repeated this

experiment six times with similar, though "not uniform results. I believe it will be "found that the air perspired consists of car"bonic gas, or fixed air, a little more than "two-thirds; of nitrogenous gas, a little less "than one-third. In one experiment, the

nitrogen made only one-fourth part of the air "collected; in another, I thought it exceeded "one-third."

He then made a series of experiments of the same kind, but substituting water for the quicksilver, sometimes heating himself previously by exercise. The results of these were not materially different from those in which he held his hand in quicksilver; but they are less clear because the carbonic acid gas given off seemed absorbed by the water. In the next series of experiments, he held his hand and arm in atmospheric air. In this case, he found that, in addition to the giving off of carbonic acid, that a portion of the oxygen of the air became absorbed. This is exactly what