CONTROL OF CULTURES 



459 



of the first tube. Occasionally a third wash was necessary to render the 

 Protozoa bacteriologically sterile. Glaser and Coria were successful in 

 sterilizing three species of ciliates and three species of flagellates by this 

 method, and later (1935) three other species of ciliates were added to 

 this list. The identifications of the organisms sterilized are uncertain, 

 except for the well-known types, Paramecium and Chilomonas. 



Another method of migration described by Glaser and Coria in their 



Fig. 124. Migration tube. 

 The tube is filled with a 

 sterile fluid to within about 

 two inches from the top. 

 Protozoa to be sterilized 

 are drawn up under the 

 sterile fluid and the small 

 tip sealed in a flame. The 

 Protozoa migrate upward 

 and are taken oflf at the top. 

 (Redrawn from Glaser and 

 Coria, 1930.) 



1930 paper was one employing a V shaped tube (Fig. 125), filled with 

 Noguchi's semisolid medium. The larger arm of the tube measured 12 

 cm. in length and had an inner diameter of 28 mm. The smaller arm was 

 9 cm. in length with an inside diameter of 8 mm. After sterilization, the 

 tube was filled with 15 ml. of sterile melted medium and this was al- 

 lowed partially to solidify. Then the contaminated culture was placed at 

 the bottom of the tube by injection through the small arm with a long, 

 fine pipette. Air bubbles were excluded. The tube was then allowed to 

 stand at room temperature for a sufficient time for some of the Protozoa 

 to reach the top of the large arm, from the surface of which they were re- 

 covered. 



