288 RESEARCH IN PROTOZOOLOGY 



and strained through gauze to remove the coarser particles. The 

 filtrate is centrifuged at a speed of between 1200 and 1500 revolu- 

 tions per minute for ten to fifteen seconds. The supernatant fluid 

 is poured off and the sediment is w^ashed and re-v^hirled at the 

 same rate from one to three times, depending upon the amount 

 of fine, Hght material to be eliminated. The final sediment may be 

 mixed v^ith vi^ater, spread upon a slide, and examined without 

 using a coverslip. 



Noller and Otten (1921) employ flotation with a salt solution. 

 A portion of stool about the size of a pea is mixed with saturated 

 salt solution, adding the saHne drop by drop until a homogeneous 

 mass is obtained. This is poured on a strainer (0.2 of a centimeter 

 mesh) and is forced through by pouring on saturated saline and 

 at the same time stirring the mixture. The filtrate is poured into 

 Erlenmeyer flasks of capacities varying from 25 to 200 cubic 

 centimeters according to the quantity of stool available. The fluid 

 should come up into the neck of the flask. The proportion of feces 

 to salt solution varies from one to eight to one to twenty, but may 

 be as high as one to 400 without materially affecting the result. 

 The flask with its contents is allowed to stand for from twenty- 

 five to ninety minutes. Then a portion of the surface is removed 

 with a platinum loop 0.3 to 0.4 of a centimeter in diameter and 

 is examined on a slide under the microscope. 



Vajda (1922) has described a method for the detection of 

 helminth ova that can be used equally well for coccidia. He uses 

 glycerin to increase the specific gravity of the oocyst-containing 

 fluid. A watery suspension of feces is treated with from one to 

 three parts of glycerin (sp. gr. 1.25) and is well mixed. The 

 coccidia rise to the surface from which they may be removed with 

 a glass rod. Refinements of this method call for a straining of the 

 feces-glycerin mixture through linen cloth, centrifugation at a 

 moderate speed for from fifteen to twenty minutes, and a mixing 

 of the sediment with from one and one-half to three parts of 

 glycerin. The author suggests removal of the floating organisms 

 for examination as follows : Fasten filter paper by means of a 

 string at the mouth of a test-tube and dip it into the feces-glycerin 

 mixture until the whole surface of the filter paper touches the 

 surface of the liquid. This method of diagnosis can be easily 

 adapted for purposes of concentrating large quantities of oocysts. 



Sheather (1923) has devised a method combining sugar flota- 



