PUTREFACTION AND INFECTION. 49 



rough handling of late. His reasoning has heen criti- 

 cised, and experiments counter to his have been adduced 

 in such numher and variety, and with such an appear- 

 ance of circumstantial accuracy, as to render the evi- 

 dence against him overwhelming to many minds. This, 

 I have reason to know, has been the effect wrought, not 

 only upon persons untrained in science, but also upon 

 biologists of eminence both in this country and America. 

 The state of medical opinion in England is correctly 

 described in a recent number of the ' British Medical 

 Journal,' where, in answer to the question, ' In what way 

 is contagium generated and communicated ? ' we have 

 the reply that, notwithstanding ' 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 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 favour- 

 able conditions, spring into existence de novo.^ 



With a view to the possible diminution of the un- 

 certainty thus described, I beg without further preface 

 to submit to the Royal Society, and especially to those 

 who study the etiology of disease, the following descrip- 

 tion of the mode of procedure followed in this inquiry, 

 and of the results to which it has led. 



§ 2. Method of Experiment. 



A chamber, or case, was constructed, 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 slides are inserted two panes of 

 glass, facing each other. The top is perforated in the 



