HABITAT OF DISEASE GERMS. 26 



opened up the land, as agriculture improved and drain- 

 Sige of the soil became general, it gradually disappeared, 

 until in this century it had become limited to the low 

 lands of Norfolk and Huntingdonshire, and in these, as 

 a consequence of still more perfect drainage, it is becom- 

 ing yet more rare, and always less fatal. 



Notwithstanding all this, the limit where microbes 

 cannot exist has not been discovered. Possibly there 

 may be some line in the northern and southern hemi- 

 spheres beyond which micro-organisms are not found in 

 the atmosphere, although it is difficult to suppose, in- 

 deed it cannot be supposed, that they do not exist on 

 the earth wherever higher forms of animal life are in 

 existence. They may not be as numerous nor as full of 

 vitality, and hence not as dangerous, but they are there. 

 At the same time, if we wish to propagate them we find 

 that the most favorable conditions are warmth, mois- 

 ture, and frequently a deficiency of sunlight. It is too 

 much a custom among Americans to close up their 

 houses, excluding light and air alike. But what I have 

 said shows the folly of such habits. Sunlight purifies 

 the air, and while it aids the higher forms of vegetation, 

 it is apt to destroy fungoid growths : not, however, by 

 its direct influence, which is always salutary, but by 

 withholding the moisture that is necessary to micro- 

 organic production. 



Microbes die out when dried up, but the germs do not. 

 They will sprout and grow, because all microbes shed 

 germs or seeds which remain dormant in a dry state, 

 like seeds or yeast cakes. This explains why cholera, 

 yellow fever, small-pox, and many contagious diseases 

 can be carried around in the air and in old clothing. 

 Those germs will grow again just as soon as they find 

 the proper temperature, moisture, and seed-bed which 

 are necessary for their development and growth. Where 

 there are weeds there are seeds, and where there are 

 microbes there are germs. 



Throw a wet dress into a trunk, and mildew or some 

 form of fungus will form upon it. Hang it above the 



