THE CULTIVATION OF ENDAMCEBA HISTOLYTICA 175 



can in most of the other media that have been evolved. The follow- 

 ing media have all been found efficient in culturing E. histolytica 

 in the writer's hands : 



Medium No. i. Locke-Scrum Mcdiian. This medium consists of a mix- 

 ture of Locke's solution and either inactivated human, horse, or rabbit 

 blood serum. Inactivated human blood serum has been found to give the 

 best results and this serum should not be over forty-eight hours old when 

 used. 



The Locke's solution used has the following formula : 



Sodium chloride 9.00 gms. 



Calcium chloride 0.24 gm. 



Potassium chloride 0.42 gm. 



Sodium bicarbonate 0.20 gm. 



Dextrose 2.50 gms. 



Distilled water 1000.00 c.c. 



This solution is filtered and autoclaved at fifteen pounds pressure for 

 fifteen minutes, and allowed to cool. There is then added one part of inacti- 

 vated human blood serum to each seven parts of the Locke solution used. 

 After adding the blood serum the mixture is filtered through a Berkefeld 

 filter and it is sometimes necessary to filter through two or more candles 

 before the mixture comes through perfectly clear. After the filtration 

 the medium is tubed, placing about ten cubic centimeters in each tube, and 

 incubated for twenty-four or thirty-six hours to determine sterility. If 

 found sterile the tubes should be kept in an incubator at 37° C. until used. 

 The reaction of the medium does not need adjusting. The addition of a 

 little rice starch, as recommended in the description of the media of Dobell 

 and Laidlaw, adds to the efficiency of this medium. A small amount of the 

 sterilized starch may be added to the culture media at the time of the 

 inoculation of the material to be cultured. The blood serum is inactivated 

 by heating at 56° C. for one-half hour. 



Medium No. 2. Ringer-Scrum Medium. The Ringer solution used in this 

 medium has the following formula : 



Sodium chloride 8.00 gms. 



Calcium chloride 0.20 gm. 



Potassium chloride 0.20 gm. 



Distilled water 1000.00 c.c. 



This solution is filtered, sterilized, and to each seven parts of it is added 

 one part of human blood serum inactivated by heating at 56° C. for one-half 

 hour. After adding the serum the mixture is filtered through a Berkefeld 

 filter, tubed, and kept in the incubator at 37° C. for twenty-four to forty- 

 eight hours to determine sterility. The tubes should be stored in the 

 incubator at this temperature until inoculated, and incubated at the same 

 temperature. 



