196 PATHOGENIC BACTERIA. 



It is said that considerable convenience in the blood- 

 serum manipulations is secured by the addition of neu- 

 trose, which prevents it coagulating when heated. It can 

 then be sterilized like bouillon and when used can be 

 solidified by the addition of agar-agar. 



Fresh blood-serum can be kept on hand in the labora- 

 tory, in sterile bottles, by adding an excess of chloro- 

 form. In the process of coagulation and sterilization the 

 chloroform is evaporated and the serum is unchanged by 

 its presence. 



Loffler's blood-serum mixture, which seems rather 

 better for the cultivation of some species than the blood- 

 serum itself, consists of 1 part of a beef-infusion bouillon 

 containing 1 per cent, of glucose and 3 parts of liquid 

 blood-serum. After being well mixed this is distributed 

 in tubes, and sterilized and coagulated like the blood- 

 serum itself. Most organisms grow more luxuriantly 

 upon it than upon either plain blood-serum or other 

 culture-media. Its special usefulness is for the Bacillus 

 diphtheriae, which grows upon it with rapidity and with 

 quite a characteristic appearance. 



Alkaline Blood-serum. — According to Lorrain Smith, 

 a very useful culture-medium can be prepared asibllows: 

 To each 100 c.cm. of blood-serum add i-r.5 c.cm. of a 10 

 per cent, solution of sodium hydrate and shake it gently. 

 Put sufficient of the mixture into each of a series of test- 

 tubes, and, laying them upon their sides, sterilize like 

 blood-serum, taking care that their contents are not 

 heated too quickly, as then bubbles are apt to form. 

 The result should be a clear, solid medium consisting 

 chiefly of alkali-albumins. It is especially useful for 

 the bacillus diphtheriae. 



Deycke's Alkali-albuminate.— 1000 grams of meat are 

 macerated twenty-four hours with 1200 c.cm. of a 3 per 

 cent, solution of potassium hydrate. The clear brown fluid 

 is filtered off and pure hydrochloric acid carefully added 

 while a precipitate forms. The precipitated albuminate 

 is collected upon a cloth filter, mixed with a small quan- 



