260 BACTERIOLOGY. 



It is easily detected microscopically in the secretions 

 of acute gonorrhoea. In secondary lesions and in very 

 old, chronic cases it is difficult of detection and fre- 

 quently eludes all efforts to find it. It is stained by the 

 ordinary methods, but perhaps most satisfactorily with 

 the alkaline solution of methylene-blue. Most impor- 

 tant as a differential test is its failure to stain by the 

 method of Gram. (How does this compare with the 

 behavior of the other pyogenic cocci when treated in 

 the same way ?) 



It does not grow upon the ordinary nutrient media, 

 and has only been isolated in culture through the em- 

 ployment of special methods. Its growth under arti- 

 ficial circumstances seems to depend upon some par- 

 ticular nutrient substance that is supplied by blood or 

 blood-serum, and in all the media that have been suc- 

 cessfully used for its cultivation this substance is 

 apparently an essential constituent. By the majority 

 of investigators it is thought that only human blood 

 possesses this important ingredient. 



It was first isolated in culture by Bumm, who used 

 for this purpose coagulated human blood-serum ob- 

 tained from the placenta. 



Wertheim improved the method of Bumm by using 

 a mixture of equal parts of sterile human blood-serum 

 and ordinary sterilized nutrient agar-agar, the latter 

 having been liquefied and kept at 50'' C. until after 

 the mixture was made, when it was allowed to cool and 

 solidify. 



Other investigators have substituted for human blood- 

 aerum certain pathological fluids from the human body, 

 such as ascites fluid, fluid from ovarian cysts, and serous 

 effusions from the pleura and from the joint-cavities. 



