42 METHODS OF CULTIVATION OF BACTERIA 



blood serum are mixed with one part ordinary neutral peptone 

 bouillon made from veal with 1 per cent, of grape sugar added 

 to it. Though this is the original formula, it can be made from 

 ox or sheep serum and beef bouillon without its qualities being 

 markedly impaired. Sterilise by method B (4) as above (p. 30). 



Alkaline Blood Serum (Lorrain Smith's Method). To each 

 100 c.c. of the serum obtained as before, add 1 to 1'5 c.c. of a 

 10 per cent, solution of sodium hydrate and shake gently. Put 

 sufficient of the mixture into each of a series of test-tubes, and, 

 laying them x on their sides, sterilise by method B (2). If the 

 process of sterilisation be carried out too quickly, bubbles of gas 

 are apt to form before the serum is solid, and these interfere with 

 the usefulness of the medium. This can be obviated if the serum 

 be solidified high up in the Koch's steriliser, in which the water 

 is allowed only to simmer. In this case sterilisation ought to go 

 on for one and a half hours. A clear solid medium (consisting 

 practically of alkali-albumin) is thus obtained, and is of value 

 for the growth of the organisms for which Koch's serum is used, 

 and especially for the growth of the b. diphtherias. Its great 

 advantage is that aseptic precautions in obtaining blood from the 

 animal are not necessary, and it is easily sterilised. 



Marmorek's Serum Media. There has always been a diffi- 

 culty in maintaining the virulence of cultures of the pyogenic 

 streptococci, but Marmorek has succeeded in doing so by growing 

 them on the following media, which are arranged in the order of 

 their utility : 



1. Human serum 2 parts, bouillon 1 part. 



2. Pleuritic or ascitic serum 1 part, bouillon 2 parts. 



3. Asses' or mules' serum 2 parts, bouillon 1 part. 



4. Horse serum 2 parts, bouillon 1 part. 



Human serum can be obtained from the blood shed in 

 venesection, the usual aseptic precautions being taken. In the 

 case of these media, sterilisation is effected by method B (4), and 

 they are used fluid. 



Serum Media for Gonococcus. The two following media 

 will be found suitable. Wertheim's medium consists of one part 

 of sterile human serum (conveniently obtained from placental 

 blood) and two parts of agar. The agar is sterilised, and fluid 

 is allowed to cool to 40 C. ; the serum warmed to the same 

 temperature is then added, and the mixture is allowed to solidify 

 in the sloped position. 



Gurd's medium is a 2 per cent, agar with acid reaction + 6 

 to phenol-phthalein (p. 34), with defibrinated human blood added 



