COCCIDIOSIS IN BIRDS AND MAABIALS 



293 



determinations, the original "pour-off" is centrifuged, decanted, 

 and whirled with salt solution just as the original sample until 

 two negative coverslips are demonstrated. The sum of the oocysts 

 counted in sample and pour-oft* is multiplied by three (oocysts 

 were counted from ^-^oths of two grams) the result being ex- 

 pressed as "oocysts per gram." If the specimen was obtained from 

 a thoroughly mixed twenty- four hour sample, the figure obtained 

 may be multiplied by the weight of the stool and expressed as 

 "oocysts per day." 



All of the apparatus for this technique, centrifuge, cups, tubes, 

 and coverslips, designed according to Lane's specifications, may be 

 obtained from R. B. Turner and Company of London. A satis- 

 factory assembly may be obtained in this country at no greater 

 expense and at a considerable saving of time. 



The ninety cubic centimeter Erlenmeyer flask may be readily 

 made by invaginating the bottom of a 100 cubic centimeter Pyrex 

 flask. This is done by provid- 

 ing the flask with a one-hole 

 rubber stopper. A short glass 

 tube (three or four centi- 

 meters long) penetrates the 

 rubber stopper and is attached 

 to a rubber tube of a con- 

 venient length that will reach 

 the mouth. Heat is applied to 

 the bottom of the flask, first 

 as a carbonizing flame and 

 later as a blast. When the bot- 

 tom begins to soften and ap- 

 pear red the flask is removed 

 from the flame, and a negative 

 pressure is created within by 

 suction on the rubber tube. 

 The bottom is raised about one 

 centimeter (see Fig. 19, C). 

 The flask is then annealed and 

 cooled. It is calibrated either 



with water or mercury. The ninety cubic centimeter mark should 

 come just to the base of the neck as indicated in Figure 19, C. 

 If it comes below or above, the flask must be reheated and 



yia. 



R- 



i 



I 

 I 



-in 



Edge ground to 

 plane surface 



Ml 



Fig. 19. — Special apparatus for 

 use in modified Lane direct centrif- 

 ugal flotation method of counting 

 oocysts. For explanation see text. 



