DUST AND DISEASE. 41 



my words might then have betrayed. But since the 

 time referred to nothing has occurred to shake my 

 conviction of the truth of the theory. Let me briefly 

 state the grounds on which its supporters rely. From 

 their respective viruses you may plant typhoid fever, 

 scarlatina, or small-pox. What is the crop that arises 

 from this husbandry ? As surely as a thistle rises from 

 a thistle seed, as surely as the fig comes from the fig, 

 the grape from the grape, the thorn from the thorn, 

 so surely does the typhoid virus increase and multiply 

 into typhoid fever, the scarlatina virus into scarlatina, 

 the small-pox virus into small-pox. What is the con- 

 clusion that suggests itself here ? It is this : That 

 the thing which . we vaguely call a virus is to all 

 intents and purposes a seed. Excluding the notion 

 of vitality, in the whole range of chemical science 

 you cannot point to an action which illustrates this 

 perfect parallelism with the phenomena of life — this 

 demonstrated power of self-multiplication and repro- 

 duction. The germ theory alone accounts for the 

 phenomena. 



In cases of epidemic disease, it is not on bad air or 

 foul drains that the attention of the physician of the 

 future will primarily be fixed, but upon disease germsj^ 

 which no bad air or foul drains can create, but which 

 may be pushed by foul air into virulent energy of repro- 

 duction. You may think I am treading on dangerous 

 ground, that I am putting forth views that may interfere 

 with salutary practice. No such thing. If you wish to 

 learn the impotence of medical practice in dealing with 

 contagious diseases, you have only to refer to the Har- 

 veian oration for 1871, by Sir William GrulL Such dis- 

 eases defy the physician. They must run their course, 

 and the utmost that can be done for them is careful 

 nursing. And this, though I do not specially insist 



