THE BIOLOGY OF MICROBES, ETC. 155 



when growing in a fluid the pellicle falls to the 

 bottom, and soon a new pellicle is formed.' This 

 microbe may be readily obtained by exposing a 

 previously sterilised infusion of hay to the atmo- 

 sphere for a short time : the spores being always 

 present in the air. On plate-cultivations, white 

 rounded colonies formed, which frequently give rise 

 to radiating processes. On potatoes and agar-agar 

 B. subtilis forms a moist, cream-coloured layer, 

 which ultimately becomes granular and dry. It 

 grows on blood serum and nutrient gelatine, both of 

 which it liquefies. B. subtilis is a motile microbe, 

 and is best cultivated at a temperature of about 

 30 C. This microbe can withstand a temperature 

 of 1 8 C. ; x and its spores have been proved to 

 have a remarkable power of resisting the influence 

 of high degrees of heat. For instance, a short ex- 

 posure to 100 C. does not destroy the vitality of the 

 spores. However, an E.M.F. of 2'72 volts destroys 

 both the spores and bacilli.^ The action of ozone 3 

 on both the spores and bacilli is that they are com- 

 pletely destroyed ; this fact explains the absence of 

 this and other microbes in the air at sea the latter 

 containing an appreciable amount of ozone. 



Bacillus ethaceticus. This small bacillus (1*5 to 

 5'1 x 0*8 to 1*0 /A) was discovered by Dr. P. F. 

 Franklaud, F.E.S., 4 and has the power of decompos- 



1 Griffiths in Proceedings of Royal Society of Edinburgh, 

 vol. xvii. p. 263. 

 a Griffiths, ibid., vol. xv. p. 45. 



3 Griffiths' Researches on Micro -Organisms, p. 184. 



4 Proceedings of Royal Society of London, vol. xlvi. p. 345. 



