228 RESEARCH IN PROTOZOOLOGY 



water) was substituted for the 0.5% salt solution and human 

 or horse serum or Loeffler's dehydrated blood serum (eight grams 

 to 100 c.c. of distilled water) added; pig serum proved un- 

 satisfactory. Cultures were maintained for over fifty-four days 

 at 36° C, transplants being made usually at three-day inter- 

 vals. Trophozoites were sometimes present in a culture at the 

 end of seven days but their number usually decreased rapidly after 

 three days. The addition of a minute quantity of sterile rice starch 

 was found to be favorable for the growth of the balantidia and 

 was ingested by them with avidity. A pure line was obtained by 

 picking out single specimens with a micropipette, placing them in 

 a drop of culture medium on a coverslip and dropping this into 

 culture tubes. 



B. coli from the pig was also cultivated by Jameson (1927). He 

 found the Boeck and Drbohlav (1925) medium for the cultiva- 

 tion of Endainocha histolytica, as modified by Dobell and Laidlaw 

 (1926), to be most satisfactory. This consists of inspissated horse 

 serum with Ringer's solution, normal saline (0.9%), or Ringer's 

 solution with the addition of ^gg albumen as liquid constitu- 

 ent. The addition of ^gg albumen is particularly favorable for 

 starting a culture but plain Ringer's solution is superior for main- 

 taining the culture. Difficulty was experienced in starting cultures 

 without the presence of sterile rice starch ; this substance, accord- 

 ing to Jameson, inhibits the growth of Blastocystis, a common in- 

 testinal fungus, which is detrimental to the balantidia. The hydro- 

 gen-ion concentration of the culture medium is important ; at a pH 

 of 5.0 or below, the organisms die and a pH of over 8.0 is unfavor- 

 able. Unfavorable bacteria may be eliminated from cultures by the 

 addition of a few drops of a i in 10,000 solution of acriflavine, 

 and dirty cultures clear up if argyrol is added so as to produce a 

 strength of i in 2000. 



Balantidia from the guinea-pig have been cultivated by Rees 

 (1927) and Scott (1927). Rees found this to be more difficult 

 than with balantidia from pigs, but finally succeeded with the same 

 medium. Guinea-pig balantidia are more active in cultures than 

 in the cecal material taken directly from the animal. They ingest 

 starch readily and resemble the balantidia from the pig in appear- 

 ance. Cysts were noted in tubes from which trophozoites had dis- 

 appeared, indicating that encystment occurred in the cultures. Scott 

 used Locke's, Ringer's or 0.75% NaCl solutions for cultivating 



