AND IN EPIDEMICS. 57 



quently electrical relations to the polarized vesicles of a 

 marsh mist, that mist, imbued with moisture, enriched by 

 the terrestrial exhalations, and screened by the shadows of 

 night, may form the most fruitful floating soil for the in- 

 visible cells of microscopic cryptogami: so that from the 

 damp earth or the nebulous air, or both, may come out to 

 propagate disease, the cells of an anomalous vegetation. 



But it may be reasonably objected, that if these things 

 do grow at night, they should, sometimes at least, taint the 

 day-air of their vicinity, from which they can scarcely be 

 entirely eliminated by an absorbing earth or a dissipating 

 mist. It might be enough to say that, if they have elec- 

 trical relations to the mist, or ascend only during the night, 

 the quantity necessary to produce morbid results may 

 .not remain during the day, but the study of the habitudes 

 of the fungi has revealed other reasons for the diurnal 

 changes of salubrity in malarious regions. 



In the first place, let me say, that no other vegetables 

 are so strictly limited as these, as to existence or proper- 

 ties, by apparently slight changes in their relations to ex- 

 trinsics, and yet their germs resist causes of destruction 

 of the most active nature. Boiling water, many of the 

 acids and caustic ammonia fail to destroy them, and they 

 sustain the cold of solid carbonic acid* (Cagniard de la 

 Tour) without the abatement of their productive power. 



Dutrochet found that by slightly acidulating a weak so- 

 lution of the albumen of an egg, various monilia were pro- 

 duced, but that when it was made alkaline the genus 

 Botrytis appeared. On a, neutral or simple solution, no 

 fungi showed themselves. 



The torula cerevisise, or yeast plant, grows in one form 



* Minus 118 F. 



