COCCIDIOSIS IN BIRDS AND MAMMALS 291 



1926a) contain details concerning technique and accuracy. A 

 synopsis of the method is given below (Stoll and Hausheer, 1926, 



p. 82). 



"For dilution egg counting one or more grams of stool, weighed 

 by difference, are put into a tube marked so that decinormal sodium 

 hydroxide may be added to secure a ratio of one gram of feces to 

 fifteen cubic centimeters total mixture with the diluent. Usually 

 three grams are weighed into a tube marked at forty-five cubic 

 centimeters ; five grams raised to seventy-five cubic centimeters 

 have also been recommended and employed for field use, the 

 larger amount helping to reduce any percentage weighing error 

 in routine. After adding the diluent, glass beads are introduced 

 to assist in comminution, the tube is rubber-stoppered, and shaken 

 thoroughly, to secure, first, a complete setting free of the ova from 

 the fecal constituents, second, a homogeneous suspension of the 

 eggs in the mixture. By means of an accurately calibrated pipette 

 150 cubic millimeters (.15 of a cubic centimeter) of the mixture 

 is immediately transferred to a slide, and the ova counted with the 

 aid of a coverslip of appropriate size to cover the drop. Originally 

 22 x 40 millimeter covers were suggested and have been used in 

 this study ; 24 x 40 millimeter covers have also been used in rou- 

 tine ; 24 X 50 and 35 x 50 have occasionally been employed. A 

 mechanical stage and the low power of the microscope (usually 

 I ox ocular and 16 millimeter objective with drawtube length of 

 160 millimeters, producing an enlargement of 100 diameters) were 

 used in making the counts. According to the dilution and drop 

 size the number of ova on the slide represents theoretically 

 i/iooth the number per gram of original feces; in practice not 

 less than two sKdes are counted to secure an average result, as is 

 usual in dilution methods." 



An alternative technique is a modification of the direct centrif- 

 ugal flotation method devised by Lane. (See papers published 

 1922, 1924, 1924a, and 1925.) As used by the writer for cat and 

 dog coccidia, the steps in the procedure are as follows : two grams 

 of stool (three grams may be used if the infection is very light, or 

 one gram or less may be used if the number of oocysts is so high 

 that it is difficult to count them from a two gram suspension) is 

 weighed into a dry Erlenmeyer flask which is caHbrated at ninety 

 cubic centimeters on the neck. Formed or soft stools are easily 

 handled with tongue depressor blades and six-inch applicator 



