MEASUREMENT OF SPERM MOTILITY 



45 



ture is counted on a separate register. The aperture is now made 

 somewhat larger (equivalent to 15 microns </> in the sample), to en- 

 sure that, in most cases, more than one spike of a rotating head 

 will be seen. Provisions are made to (1) close the detector as soon as 

 the velocity of a cell is classified, in order to prevent interference 

 from an eventual third or fourth flash of the head, (2) reset the scale 

 of 2 if only one flash is seen (e.g., by passage at the edge of the aper- 

 ture), (3) close the detector if the background of the sample rises too 

 high as when agglutinated cells or pieces of dirt drift by, and (4) 

 measure the elapsed time the detector is open to give signals to the 

 discriminator. In this respect the apparatus resembles somewhat that 

 of Bosselaar and colleagues (1952, 1955). 



Calibration of the accuracy of the apparatus was made by compar- 

 ing the data with the absolute figures obtained from dark field-track 

 photographs taken with an exposure time of 1 sec of the same slide 

 directly after the electronic measurement was performed. The velocity 

 of the sperm can be determined from the length of the track made 

 during this time, after appropriate correction (see Rikmenspoel, 

 1957b, p. 43). The results of this calibration are given in Figs. 12 and 



o 



(0 



\ 

 zL 



of 



UJ 



I- 



o 



</) 



UJ 



I- 

 l> 



150 



100 



50 100 150 



V PHOTOGRAPHIC, JJL/SEC. 



Fig. 12. Mean velocity of semen samples as measured with the elec- 

 tronic analyzer and from photographs. 



