685 



PAKT VI. 



DISTRIBUTION AND HABITAT OF THE BACTERIA. 



NUMEROUS forms of bacteria grow in the most various General 

 surroundings of mankind, whenever they meet with O f & the u 

 sufficient moisture, nutritive material, and a temperature bacteria - 

 of at least 6 to 10 C., and they multiply the more 

 quickly the nearer the temperature approaches the aver- 

 age optimum of 20 to 30 C., and the better and more 

 plentiful the nutritive material. Wherever dead organic 

 materials, excreta of man and animals, dead bodies, dead 

 plants, household refuse, &c., accumulate on the surface 

 of the ground, in stagnant or running water, or within 

 dwelling-houses, in the presence of sufficient moisture 

 and temperature, bacterial growth occurs, and ultimately 

 occasions the complete destruction of these materials, 

 the place of which is taken by an enormous number of 

 newly-formed individuals. 



In view of the distribution, the enormous capacity for 

 multiplication, and the relatively great resisting power of 

 the bacteria, one involuntarily inquires as to the means 

 which come into play in nature in order to destroy the 

 masses of bacteria which are being constantly formed, 

 and to provide against their accumulation in too great 

 numbers. The cold of winter is not the active agent, 

 for, as is well known, it only occasions an arrest of de- 

 velopment, and appears to preserve all the bacteria in a 

 living state. The natural means of disinfection is in The natural 

 the first place drying of the bacteria ; then exhaustion of SaSection. 

 the nutritive substrata ; at times also high temperatures, 

 more especially on the surface of the soil from the solar 

 heat. These various agents in truth only kill the less 

 resistant vegetative forms, while the majority of the per- 

 manent forms retain their vitality in a dry state, and 



