18 THE FLOATING-MATTEE OF THE AIR. 



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 de terminer ces quelques lignes que je 

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

 observer que vous rendriez service aux Colonies de la Grrande- 

 Bretagne en r6pandant la connaissance de ce livre, et des 

 principes que j'^tablis touchant la maladie des vers k soie. 

 Beaucoup de ces colonies pourraient cultiver le murier 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 r6gnante, mais en outre de 

 donner aux r^coltes de la soie une prosperite 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, the 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 



