OF THE ALIMENTARY TRACT 41 



missed With others they are unreliable and will un- 

 doubtedly lead to errors. 



Methods of concentration of the cysts in the stool 

 so that they may be more readily found are strongly 

 recommended by some. For this purpose the pro- 

 cedure of Yorke and Adams (1926) is recommended. 



About 10 grams of the feces, thoroughly mixed with 

 200 cc. of distilled water, is allowed to stand for 20- 

 30 minutes. The supernatent fluid is poured off and 

 distilled water to 500 cc. added. After standing 

 overnight in the ice box the supernatent fluid of this 

 is decanted and the sediment saved. This is washed 

 once with distilled water and centrifugalized at about 

 2000 revolutions per minute for two minutes. The 

 sediment is suspended in a solution of sucrose of about 

 1.080 specific gravity in about the proportion of 2 

 cc. of sediment to 14 cc. of sucrose solution. This 

 mixture is next centrifugalized at 3000 revolutions 

 per minute for 3 minutes. The supernatent solution, 

 which contains the cysts, is concentrated by dilution 

 with three volumes of distilled water and centrifugal- 

 izing at 2000 revolutions per minute for 2 minutes. 

 A small portion of the sediment is examined for the 

 cysts in microscopic preparation with iodine solution. 



Without the intention of detracting from the ab- 

 solute value of permanent staining, concentration 

 methods and cultures, and recognizing their full 

 value where they may be used in a competent way, 

 particularly for uncovering amoebic infections when 

 the parasites are sparse, it is the desire of the writer 



