352 APPLICATION OF METHODS OF BACTERIOLOGY 



and semitranslucent by transmitted light. By reflected 

 light their surface has the appearance of frosted glass. 

 Later, if few in number, so that their growth is unimpeded, 

 the colonies may attain a diameter of 2 millimeters or 

 more, become thicker and denser, with a faintly brownish 

 tinge about their centres, and a slightly irregular outline. 



Under a low power of the microscope a fully developed 

 colony is seen to consist of a general circular expansion, 

 with thin, translucent, smooth, sharply defined margin, 

 but becoming brownish, granular, and thicker toward the 

 central portion, which is made up of coarse, granular, 

 brown-colored clumps closely packed together. 



The appearances coincide with the figure of such a colony 

 given by Wertheim. 1 



Wassermann 2 calls attention to the success he has had 

 in cultivating this organism upon a mixture of swine-serum 

 and nitrose, the latter being a commercial product chemically 

 known as casein-sodium phosphate. 



The preparation of the medium and its composition are 

 as follows: 



In an Erlenmeyer flask mix 15 c.c. of swine-serum, as 

 free as possible from hemoglobin; 30 to 35 c.c. of water; 

 2 to 3 c.c. of glycerin; and finally 0.8 to 0.9 gram (i. e., 

 about 2 per cent.) of nitrose. This is boiled, with gentle 

 agitation, over a free flame, until all ingredients are dissolved 

 and the cloudy fluid has become quite clear. After such 

 boiling the mixture can be sterilized by steam without 

 precipitating the albumen, and may then be kept indefi- 

 nitely ready for use. 



1 Deutsche med. Wochenschrif t , 1891, No. 50; Centralblatt fur Gyna- 

 kologie, 1891, No. 24. 



2 Zeitschiift fiir Hygiene und Infektionskrankheiten, Bd. xvii, p. 298. 



