CONCLUSION. 295 



constitutes contagion, could only be defined by having 

 recourse to the term " catalytic action," which merely 

 placed the solution of the problem another step back, 

 and substituted one unknown thing for another.* The 

 parasitic theory will have done much for science if it 

 only delivers us from "miasmata," "effluvia," and, 

 above all, " catalytic action." As soon as it had been 

 shown that miasmata and effluvia, as well as virus, were 

 only air-germs that is, microbes and their spores a 

 brilliant light was thrown on all pathology, of which 

 the benefits may be measured by the great work accom- 

 plished in this direction within the last ten years. 



This theory has given us Gue'rin's protective treat- 

 ment of wounds, Lister's antiseptic dressing, and 

 Pasteur's new vaccine, and these three great dis- 

 coveries are enough to render the hypothesis immortal, 

 even admitting that it is only an hypothesis. The 

 adverse theories, when opposed to the microbian 

 theory, can show us no progress effected in science, 

 and this suffices to condemn them. 



Moreover, the microbian theory is no longer in 

 the primitive stage in which it can be regarded as 

 a pure hypothesis, since it has entered the domain 

 of positive facts. Before an infectious disease can be 

 considered due to the presence of a specific microbe, 



* See, for example, the article Miasmes in Nysten's Dictionary 

 (Littre and Robin, edit. 1864) : " Miasma is constituted by the organic 

 substances of the air, in different stages of catalytic modification." These 

 words are printed in italics by Robin himself. See also the words 

 Efluves, Catalytiques, Virus, etc., in the same dictionary. 



