294 bactehtoloqy. 



mercial product chemically known as easein-sodiuni 

 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 haemoglobin ; 30 to 36 c.c. of water ; 

 2 to 3 c.c. of glycerin ; and finally 0.8 to 0.9 gramme 

 (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 albumin, and may 

 then be kept indefinitely ready for use. 



When needed, the flask and its contents are heated to 

 50° C. ; from six to eight tubes of 2 per cent, peptone- 

 agar-agar are dissolved by boiling, brought to 50° C, 

 and then mixed with the solution in the flask and the 

 mass poured into Petri dishes. Upon the surface of this 

 serum-nitrose-agar the cultivation is to be conducted. 

 Wassermann lays particular stress upon two points that 

 are essential to success, viz., the preliminary boiling of 

 the serum-nitrose mixture before steam sterilization, as 

 this prevents precipitation of the albumin ; and the 

 necessity of having both the serum-nitrose mixture and 

 the agar-agar, to be mixed with it, at not over 50° C, 

 for if they are at boiling temperature when mixed, or if 

 they are brought to the boiling temperature after mixing, 

 the albumin will be precipitated notwithstanding the 

 presence of the nitrose, which otherwise prevents this. 



Wassermann further observes that some samples of 

 serum require to be more highly diluted with water than 

 in the proportions given above ; that the agar-agar 

 should be feebly, but distinctly, alkaline to litmus. 



