1876.] On the Phenomena of Putrefaction and Infection. 171 



"On the Optical Deportment of the Atmosphere in reference 

 to the Phenomena of Putrefaction and Infection." By John 

 Tyndall, F.R.S. Received January 24, 1876. 



The author refers in an Introduction to an inquiry on the decomposi- 

 tion 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 sen- 

 sitive by darkness, the character of the medium in which their experi- 

 ments 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 Number of the ' British Medical Journal/ and 

 in answer to the question, " In what way is contagium generated and 

 communicated?" Messrs. Braidwood and Vacher reply that, notwith- 

 standing "an almost incalculable amount of patient labour, the actual 

 results obtained, especially as regards the manner of generation of con- 

 tagium, have been most disappointing. Observers are even yet at vari- 

 ance 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" 



"With a view to the possible diminution of the uncertainty thus de- 

 scribed, the author submits without further preface to the Eoyal Society, 

 and especially to those who study the aetiology of disease, a description 

 of the mode of procedure followed in this inquiry and the results to 

 which it has led. 



A number of chambers, or cases, were constructed, each with a 

 glass front, its top, bottom, back, and sides being of wood. At the 

 back is a little door which opens and closes on hinges, while into the 

 sides are inserted two panes of glass, facing each other. The top is per- 



