COCCIDIOSIS IN BIRDS AND MAMMALS 287 



the contents must be evacuated while the syringe is in an upright 

 position, i.e., plunger on top, outlet at bottom. 



Other methods of estimating or of counting the number of 

 oocysts in a suspension have been used. Johnson (1927) "esti- 

 mates" the number of oocysts present by direct microscopic ex- 

 amination of a very small drop (0.02 of a cubic centimeter) on a 

 slide. In a later piece of work (1927a), his method is to count 

 the number of sporulated oocysts in o.oi of a cubic centimeter of 

 a dilution of the original suspension. 



It must be realized that counts of these organisms unless made 

 on very large samples immediately before use cannot be very 

 accurate. Under the very best conditions it is probably not pos- 

 sible to exclude all non-viable oocysts from the count. Furthermore 

 it is possible that unsegmented oocysts which were not included 

 in the count may mature during their passage through the host. 

 Nevertheless, these irregularities must tend toward consistency 

 from one experiment to another. It is the writer's belief that this 

 quantitative technique with all its difficulties is of value, in that 

 it permits one observer to verify and extend the results of an- 

 other under approximately the same conditions. 



Diagnosis. There are a number of methods of diagnosing coc- 

 cidial infections, all of them based on the finding of oocysts. They 

 may be roughly divided into methods in which the material ex- 

 amined is concentrated, and the single method in which it is not. 



The simple smear method is the quickest of all methods, and, 

 except in heavy infections, it is the least accurate. An amount of 

 stool is gathered on the end of a toothpick and is rubbed up in a 

 drop of saline or water on a slide. A coverslip is dropped on this 

 suspension. The completed preparation should be just thin enough 

 to permit the reading of newspaper print through it. The entire 

 area under the coverslip is examined, and in the event of a nega- 

 tive finding, one or two more similar preparations should be ex- 

 amined. 



All other methods of diagnosis depend upon a concentration of 

 the material examined. Concentration is accomplished either by 

 centrifugation, by an increase in the specific gravity of the mate- 

 rial containing oocysts, or by a combination of centrifugation and 

 flotation. 



Davis and Reich (1924) mix the fecal specimens with water 

 and allow them to soften if they are hard. They are then washed 



