This is one of those bold, and, we believe, successful reasonings from analogy which were very characteristic of Abernethy. The truth is, that even the experiments of Edwards, some of which were, a long time since, repeated by ourselves, with the same results, are not, I conceive, so conclusive as the analogy of Abernethy. It is true, they consisted of placing frogs and other animals in gases not containing oxygen, when it was found, notwithstanding, that there was no diminution in the quantity of the carbonic acid produced, and which therefore could not have been compounded of any oxygen in the gas. But even here many possible sources of fallacy suggest themselves. The previous expulsion of all the oxygen from the animal is obviously a matter of uncertainty. There are, besides, those sources of fallacy which are inseparable in some form or other from all experiments on animals which disturb their natural habits, especially when these disturbances are so great as to amount to suffering. From all such experiments Abernethy instinctively shrunk. His repulsion to them seems not to have rendered it necessary to him to have shown that they were as physiologically inconclusive as they were morally questionable. At all events, his present experiments were not obscured by any such sources of fallacy.
Still the idea of the carbonic acid exhaled by the lungs, being made up of the union of the carbon exhaled with the oxygen taken in, continued to be very extensively entertained. We can only say that to us it seems entirely a child of the imagination; what Horace calls
"Mentis gratissimus error;"
and shows not only how few people can find leisure to investigate, but how few venture to observe or think for themselves. Abernethy also experimented by holding his hand in carbonic acid, when he found that in about nine hours, three ounces, by measure, of carbonic acid were absorbed by the skin; and in the remaining gas, a considerable quantity of other gas which had been given off, which appeared to be nitrogen.
Desirous of ascertaining the quantity of carbonic acid gas given off by his hand, in different gases in a single hour, he introduced his hand into various gases. In the experiment with
| Drs. | |
| Nitrous oxide, there came off | 6 |
| Hydrogen | 4 |
| Atmospheric air | 3 |
The test for the carbonic acid was, as before, in all cases, lime-water. He also found that the skin absorbed oxygen much more readily than most other gases. One remarkable experiment we will notice, to show how laborious all these investigations were, and for the interesting nature of the result. He placed his hand alternately in vessels containing each twenty-four ounces, by measure, of nitrogen and oxygen gases. After eight hours' exposure in each, two-thirds of the oxygen had disappeared, whereas only one twentieth of the nitrogen was absorbed. Indeed, there is no one feature of these experiments perhaps more interesting than those which suggest the stronger aptitude of the skin to absorb oxygen in comparison with other gases. For example, Abernethy found that the skin absorbed, by measure,
| Ozs. | |
| Of oxygen gas, in eight hours | 8 |
| Of nitrous gas, in five hours | 3 |
| Of hydrogen, in five hours | 1½ |
| Of nitrogen, in eight hours | 1 |
Mr. Abernethy then made some experiments on his own lungs, after the manner that Mr. Cruikshank had done, to find the quantity of water exhaled, by breathing into glass jars filled with and inverted in quicksilver, and by other methods, and also to ascertain the change produced in the air by respiration. These are all interesting; but we can only give general results, referring to the work itself, as full of material for thought and future observation. He considered that, on the whole, the change in the air was, that in one hundred parts, consisting of