BACILLUS SUBTILIS. 897 



colonies, which, under a low power, have a yellowish- 

 brown colour, and an irregular margin, with numerous 

 hair-like processes projecting from it. At a later period 

 a narrow clear zone appears around the dark centre, 

 and beyond this there is a greyish layer consisting of 

 a circle of rays. At the same time the gelatine is 

 energetically liquefied. On agar a thick wrinkled skin 

 is formed. On potatoes thick yellowish-white deposits 

 appear, which, on the second day, have a moist satin- 

 like appearance, with dry, whitish spots at parts of the 

 surface, soon extending .over the whole extent of the 

 layer ; ultimately the cultivation appears as if powdered 

 with a white granular mass. 



These bacilli require plenty of oxygen, and growth, Necessity fo 

 multiplication, and spore formation only go on in a 

 normal manner when there is no hindrance to the 

 access of air ; in vessels devoid of air no development 

 visible to the naked eye takes place. Under unfavour- 

 able conditions of life the bacillus subtilis forms the 

 most various kinds of involution forms, flasklike 

 swellings, &c., which, under the microscope, show 

 a peculiar fatty appearance. According to Buchner Involution 

 these involution, forms appear especially when the orms ' 

 amount of sugar in the nutrient solutions is markedly 

 greater than the amount of nitrogen. The same author 

 found that even slight variations in the composition of 

 the nutrient substratum occasion certain alterations in 

 form, and more especially alterations in thickness of the 

 bacilli. 



Bacillus subtilis does' not appear to exercise any Action on ti 

 special fermentative action, more especially with reference stratum* 8Ul 

 to the carbo-hydrates ; the reason why such properties 

 were formerly ascribed to bacillus subtilis was evidently be- 

 cause it was confounded with bacillus butyricus and other 

 bacteria. Vandervelde has recently asserted that bacillus 

 subtilis can set up fermentation when it is compelled to 

 exist without oxygen. Vandervelde tried to show this 

 by careful analysis of the nutrient substratum in which 

 a pure cultivation of bacillus subtilis had grown for a 

 considerable time ; he found that glycerine or grape 



