THE CULTIVATION OF INTESTINAL PROTOZOA 69 



In the case of Opalina, varying concentrations of human serum 

 were used, from o.i per cent up to ten per cent. In addition, follow- 

 ing the work of Rees, a sprinkling of rice starch was added to one 

 set of tubes. As some organisms grow best in the presence of 

 free oxygen, as in the upper part of the tube, and others grow 

 best with the oxygen partially excluded, the height of the column 

 of medium was varied from a few miUimeters up to twenty milli- 

 meters. In this work, four sets of tubes were inoculated. The first 

 set was plugged with cotton stoppers. The second set was plugged 

 with rubber stoppers. The third set was gently heated at the open 

 end before inserting a rubber stopper, and the fourth set was 

 heated to a much higher temperature before inserting rubber 

 stoppers. Three different temperatures were used: (a) the low 

 temperature incubator or the ice-box (this temperature is about 

 10° C), (b) room temperature, or a low temperature incubator 

 (a temperature of about 25° C), and (c) the ordinary incubator 

 (37° C). In the case of cold-blooded animals, room temperature, 

 or, more preferably, ice-box temperature, is best suited to their 

 growth. Cultures made at the warmer temperatures have to be 

 transplanted at more frequent intervals. In the case of cold- 

 blooded animals, the transplants may be made weekly, or even 

 bi-weekly. 



METHODS IN GENERAL USE IN THE CULTIVATION OF AN ORGANISM 



In the selection of a medium for the cultivation of intestinal 

 protozoa, several factors should be considered : 



(i) The simplicity of its formula. 



(2) The facility of its preparation. 



(3) The availability of its various constituents. 



(4) Its physical character, as determined by the ease with which 



portions may be removed for repeated examination. 



At present, there are in general use three main types of culture 

 media for intestinal protozoa: (i) Hogue's ovomucoid medium, 

 (2) serum-salt solution, and (3) Boeck's Locke-egg-serum 

 medium. 



These three media are used with a number of modifications. All 

 three, with their various modifications, give good growth of all 

 intestinal protozoa so far cultivated, with the exception of the 

 parasitic amoebae. In the case of parasitic amoebae, Boeck's medium 



