NUTRIENT MEDIA 39 



Chloroform is particularly suitable for the sterilisation of 

 blood-serum, as it has a powerful germicidal action com- 

 bined with a low boiling-point, so that it can be driven off 

 with certainty after sterilisation is complete. (The liquid 

 under treatment is shaken up with chloroform, and allowed 

 to stand some days, when it is freed from chloroform by 

 prolonged heating at 62 C.) 



The serum from human blood, obtained at operations 

 and from placentae, occasionally presents advantages 

 over that obtained from animals. 



Modifications of Blood-Serum. The fluid obtained 

 from hydroceles, cysts, or dropsical effusions, is practically 

 the same in composition as blood-serum. 



Loffler's Medium. Two parts of blood-serum with 

 one part of nutrient glucose broth. The medium is 

 solidified in a slanting position. 



Blood-smeared Agar. The surface of the agar in sloped 

 agar- tubes is smeared with blood obtained aseptically. 

 The tubes must not be sterilised after the blood has been 

 added. 



Egg-Albumin. The albumin from birds' eggs is care- 

 fully separated from the yolk, and treated as directed 

 under the preparation of blood-serum tubes. The white 

 from plovers' eggs yields an almost transparent medium. 

 Hens' eggs may (Hueppe) be themselves used. New-laid 

 eggs are washed in sodium carbonate solution, immersed 

 in 1 in 2,000 mercuric chloride solution for a short time, 

 thoroughly rinsed in water that has been well boiled, and 

 finally rinsed in strong alcohol and ether. The end is 

 pierced with a sterile needle, and the material to be 

 inoculated is introduced into the egg by means of a glass 

 capillary tube, from which it is blown with great care. 

 The hole is now closed with sterile cotton-wool. This 

 method of cultivation is particularly well adapted for the 

 cultivation of the anaerobic bacteria. 



Beer- Wort. Unhopped beer- wort is allowed to stand in 

 a cool place for twelve hours, filtered, steamed for one 

 hour, again filtered, and then sterilised. 



Beer- Wort Gelatin. -One hundred grammes of gelatin 

 are dissolved in a litre of unhopped beer- wort, clarified and 

 filtered, but not neutralised. 



Silica Jelly. This preparation is destitute of organic 

 matter, and is used for the organisms of ' nitrification,' 



