60 APPLIED BACTEKIOLOGY 



serum is rendered faintly alkaline and run off into testr 

 tubes, ■which are then plugged as usual, and laid on a 

 slanting surface, and the serum made to set by heating in 

 the hot-air steriliser to 75° C. The tubes can then be 

 sterilised in thfe usual way by steaming on three successive 

 occasions. We have found the above to be the most 

 easy method of preparing blood serum, and one which 

 gives perfectly satisfactory results. The serum, when so 

 prepared, should have a jelly-like consistency, and is of 

 an opalescent, yellowish-white colour. 



The serum from human blood, which is sometimes to be 

 obtained at operations and from placentae, is used by some 

 workers, but its use presents no advantages over that 

 obtained from the horse or other animals. 



Modifications of Blood Serum. — The fluid obtained from 

 hydroceles, cysts, or dropsical effusions is practically the 

 same in composition as blood serum, and the method of 

 'preparing nutrient media from it is the same as in the 

 case of blood serum. 



(18) Lofler's Medium. — This medium, which is used for 

 rapid diagnosis of diphtheria, is prepared as follows : Two 

 parts of blood serum are mixed with one part of nutrient, 

 grape-sugar broth. The tubes are then solidified in a 

 slanting position, and treated as in the case of the ordinary 

 serum tubes. 



(19) Egg Albumin. — The albumin from birds' eggs is a 

 very convenient and good medium for the growth of many 

 bacteria. The albumin is carefully 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, according to 

 Hiippe, be themselves used with advantage as nutrient 

 media. The newly-laid eggs are washed in soda solution, 

 and then laid in 1 in 2,000 mercury bichloride solution for a 



