THE CULTIVATION OF ENDAMCBBA HISTOLYTICA 177 



omission of dextrose, transfers being made every forty-eight hours. 

 The addition of rice starch, as in the Dobell-Laidlaw media, is 

 useful at times, if the amoebae appear to be decreasing in number, 

 but is not necessary as a routine procedure. Upon this medium we 

 find that the parasite will live indefinitely, and we now have a 

 strain in this laboratory that has been cultured for over three 

 years and which still is normal in morphology and produces 

 lesions in kittens. 



TecJiniqiie of Cultivation. Aseptic precautions are not absolutely 

 necessary in the inoculation of the culture media for clinical 

 diagnostic purposes, although it is best to observe such precau- 

 tions, but in making transfers it is always best to observe ordinary 

 asepsis in the technique. For diagnostic work a good-sized particle 

 of the formed feces, or several large loopsful of the liquid or semi- 

 liquid feces, is emulsified in the liquid portion of the medium, if 

 slants are used, or in the Locke-Serum medium. If the feces are 

 formed the inoculated material should be thoroughly broken up 

 in the medium with a platinum loop. After inoculation the cul- 

 tures are placed in an incubator at 37° C. for twenty-four hours 

 and then a small amount of the sediment, taken from the culture 

 with a one cubic centimeter pipette, having a rather large bore, 

 should be placed upon a microscopic slide, covered with a cover- 

 glass, and examined. If negative the culture should be replaced 

 in the incubator and re-examined at the end of another twenty- 

 four hours. 



Some authorities have not secured good results in cultivating 

 E. histolytica from the stools because they have employed ordinary 

 bacteriological technique in the examination. The amount of feces 

 inoculated into the media should be much larger than a platinum 

 loopful, the usual amount of material used for inoculating culture 

 media in bacteriological work, and it is absolutely useless to ex- 

 amine a loopful from the cultures and expect to find amoebae. A 

 one cubic centimeter pipette, wath a good-sized bore, should al- 

 ways be used in securing the sediment from the cultures for 

 examination, and at least one-tenth of a cubic centimeter should 

 be removed and examined. The amoebae are most numerous in the 

 sediment at the bottom of the tubes and upon the surface of the 

 ^gg slant at the bottom of the tubes, if the Locke-Egg-Serum 

 medium is used. The amoebae do not occur in the fluid portion of 

 the culture much above the sediment. 



