178 FKAGMENTS OF SCIENCE. 



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 demon- 

 strated power of self-multiplication and reproduc- 

 tion. The germ theory alone accounts for the pheno- 

 mena. 



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 germs, 

 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 Gull. 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 

 upon it, would favour the idea of their vital origin. For 

 if the seeds of contagious disease be themselves living 

 things, it may be difficult to destroy either them or their 



