18 THE FLOATING-MATTEE OF THE AIE. 



distinct from it, has also been investigated by Pasteur. 

 Enough, however, has been said to send those in- 

 terested in these questions to the original volumes for 

 further information. To one important practical point 

 M. Pasteur, in a letter to myself, directs attention : 



Permettez-moi cle terminer ces quelques lignes que je 

 dois dieter, vaincii que je suis par la maladie, en vous faisant 

 observer que vous rendriez service aux Colonies do la Grande- 

 Bretagne en repandant la connaissance de ce livre, et des 

 princpes que j'etablis touchant la maladie des vers a sole. 

 Beaucoup de ces colonies pourraient cultiver le mui-ier avec 

 succ^s, et, en jetant les yeux sur mon ouvrage, vous vous 

 convaincrez aisement qu'il est facile aujourd'hui, non- 

 seulement d'eloigner la maladie r^gnaote, mais en outre de 

 donner aux r^coltes de la soie une prosp^rit6 qu'elles n'ont 

 jamais eue. 



Origin and Propagation of Contagious Matter. 



Prior to Pasteur, the most diverse and contradictory 

 opinions were entertained as to the contagious character 

 of pebrine ; some stoutly affirmed it, others as stoutly 

 denied it. But on one point all were agreed. ' They 

 believed in the existence of a deleterious medium, 

 rendered epidemic by some occult and mysterious 

 influence, to which was attributed the cause of the 

 disease.' Those acquainted with our medical literature 

 will not fail to observe an instructive analogy here. 

 We have on the one side accomplished writers, like Dr. 

 Murchison, ascribing epidemic diseases to ' deleterious 

 media ' which arise spontaneously in crowded hospitals 

 and ill-smelling drains. According to them, tlie contagia 

 of epidemic disease are formed de novo in a putrescent 

 atmosphere. On the other side we have, writers like 

 Dr. Budd, clear, vigorous, with well-defined ideas and 



