GERMS: GOOD AND BAD. 



141 



some of mineral and inorganic nature, others of or- 

 ganic and living kind. It is an ocean having particles, 

 living and dead, for its floating things ; and the living 

 particles, in brief, are the " germs " whereof we hear 

 so much that is interesting in the science of the day. 

 It is true that we are encompassed about by a great 

 cloud of living particles ; but it is not true to assert 

 that these particles are all equally noxious to man or 

 equally innocuous in so far as human interests are 

 concerned. 



Some germs, like those of the blue mould, may 

 be deemed harmless 

 enough in their char- 

 acter. Others again, 

 like those of the yeast- 

 plants (fig. 29), are more 

 destructive, it is true, 

 or may be sometimes 

 pressed into the service 

 of man. That bottle of 

 claret you left uncorked 

 after dinner two days 

 ago has gone to the bad. You declare it to be as sour as 

 vinegar; and well may it be so, for vinegar it has become. 

 Into your wine from the air, there dropped sundry micro- 

 scopic germs of yeast-plants. These bred and multiplied 

 in the soil they found ready to hand in the shape of 

 the wine. Through the exercise of their own chemical 

 powers they produce vinegar by a process of fermen- 

 tation, just as certain other and nearly-related yeast- 

 germs manufacture alcohol out of sugary solutions. 



By the air also are carried the germs of diseases ; 

 and that many of our epidemics are air-borne in their 

 nature and propagation, remains a sure fact of health- 



