96 



BACTERIOLOGY 



accomplished with chloroform, of which i per cent is to be added 

 to the medium; in this manner the serum may be preserved for a 

 long time. It may be filled into tubes, solidified and sterilized 

 as required; the chloroform will be driven off by the heat, owing 

 to its volatihty. Blood-serum media which are sterilized at 

 low temperatures should be tested for twenty-four hours in the 

 incubator to prove that sterilization has been effective; if it has 

 not, development of the contaminating bacteria will take place 

 and be visible to the eye. 



Pig. 36. — Koch's serum sterilizer. 



Loffler's blood-serum consists of one part of bouillon con- 

 taining I per cent of glucose, mixed with three parts of blood- 

 serum. It is sterilized like ordinary blood-serum. It is used 

 largely for the cultivation of the bacillus of diphtheria. 



Fresh eggs in their shells may be used without other prepara- 

 tion than washing the surface thoroughly with bichloride of mer- 

 cury solution; or a^ter sterilization by steam, which of course 

 coagulates the albumen. The egg is easily inoculated through a 

 small opening made with a heated needle, which may be closed 

 afterward with collodion. Hueppe recommended eggs closed in 

 this manner for the cultivation of anaerobic bacteria. 



