On the optical deportment of the atmosphere in reference to the phenomena of putrefaction and infection

The author refers in an Introduction to an inquiry on the decomposition of vapours and the formation of active clouds by light, whereby he was led to experiment on the floating matter of the air. He refers to the experiments of Schwann, Schroder, and Dusch, Schroder himself, to those of the illustrious Prench chemist Pasteur, to the reasoning of Lister and its experimental verification regarding the filtering-power of the lungs; from all of which he concluded, six years ago, that the power of developing life by the air, and its power of scattering light, would be found to go hand in hand. He thought the simple expedient of examining by means of a beam of light, while the eye was kept sensitive by darkness, the character of the medium in which their experiments were conducted could not fail to be useful to workers in this field. But the method has not been much turned to account; and this year he thought it worth while to devote some time to the more complete demonstration of its utility. He also wished to free his mind, and if possible the minds of others, from the uncertainty and confusion which now beset the doctrine of “spontaneous generation.” Pasteur has pronounced it “a chimera,” and expressed the undoubting conviction that this being so it is possible to remove parasitic diseases from the earth. To the medical profession, therefore, and through them to humanity at large, this question is one of the last importance. But the state of medical opinion regarding it is not satisfactory. In a recent Humber of the ‘ British Medical Journal/ and in answer to the question, “ In what way is contagium generated and communicated” Messrs. Braidwood and Yacher reply that, notwithstanding “an almost incalculable amount of patient labour, the actual results obtained, especially as regards the manner of generation of contagium, have been most disappointing. Observers are even yet at variance whether these minute particles, whose discovery we have just noticed, and other disease-germs, are always produced from like bodies previously existing, or whether they do not, under certain favourable conditions, spring into existence de novo ”.