502 BACTERIOLOGY. 



granular in structure, and have a somewhat darker, 

 more compact centre, surrounded by a paler marginal 

 zone. With high magnification rows of cocci are seen 

 sprouting from the edges. In stick cultures along the 

 line of puncture minute transparent drops appear. 



Growth on Gelatin. The growth on gelatin is slow, 

 if there is any development at all, owing probably to 

 the low temperature viz., 22 to 24 C. at which the 

 gelatin has to be kept. The gelatin is not liquefied. 



Growth on Blood-serum, The growth on Ldffler's 

 blood-serum mixture is very similar to that on agar, 

 but somewhat more vigorous, appearing on the surface 

 as a delicate layer of dew-like drops. 



Growth in Bouillon. In bouillon, at the end of twelve 

 to twenty-four hours in the incubator, a slight cloudi- 

 ness of the liquid will be found to have been pro- 

 duced, due to the development of the micrococci, 

 which on microscopical examination can be seen to be 

 arranged in pairs or longer and shorter chains. After 

 two or three days the medium becomes again trans- 

 parent, owing to the subsidence of the cocci to the 

 bottom of the tube. 



Special Media. Fraenkel was the first to draw at- 

 tention to the fact that this organism soon loses its 

 reproductive power when grown on ordinary culture 

 media, and more particularly solid media. In fluid 

 media the vitality is not quite so quickly lost; but 

 even here it is found advisable in practice to transplant 

 fresh cultures every day. By this method, when bou- 

 illon cultures are used, the vitality may be indefinitely 

 prolonged; but after transplantation through several 

 generations it is found that the cultures begin to lose 

 in virulence, which finally disappears entirely. In order 



