BLOOD SERUM 41 



growth of the b. diphtheriae and may be used for other 

 organisms. It has the following composition. Three parts of 

 calf's or lamb's 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. 29). 



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 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. Dr. Lorrain Smith informs us 

 that 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 he has found it of value for the growth of the 

 organisms for which Koch's serum is used, and especially for the 

 growth of the b. diphtheriae. 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. 



Hiss's Serum Water Media. These are composed of one 

 part of ox's serum and three parts of distilled water with 1 

 per cent litmus ; various sugars in a pure condition are added in 

 the proportion of 1 per cent. The development of acid by 

 fermentation is shown by the alteration of the colour and by 



