But all animals may be said to breathe quite as much by their skin as by their lungs. Leaves, too, are the breathing surfaces of vegetables; and, therefore, to ascertain the facts in the one, without inquiring into those observable in the other, would be likely to fog our reasoning and falsify our conclusions. The first impression we obtain from all animals is from external form and appearance—from, in fact, its outward covering. It was the first organ to which Abernethy devoted his most particular attention; and here again his investigations show how little those knew of his mind who imagined that his thoughts were restricted to any one set of organs. 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 so considered. 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 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 us are in applying physiology to the correction of disordered functions, we can seldom collect for ourselves, 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 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.