MEASUREMENT OF SPERM MOTILITY 



41 



A recording of the passage of a rotating sperm cell is shown in Fig. 

 8. The flashes due to the rotation of the head are very clear; the 

 "passage" of middle piece and tail can also be distinguished. A re- 

 cording of the passage of a circularly swimming (nonrotating) cell is 

 given in Fig. 9. The absence of flashes from the head and the regu- 

 lar movement of middle piece and tail conform to the picture of 

 these cells obtained from the films. 



When a sperm cell passes over the aperture, it holds, for the dis- 

 tance covered, during the time any part of it is visible, that: 



vt = I (4) 



where v is the velocity of the cell and / the duration of the passage. 

 The distance / is essentially equal to the length of the cell plus the 

 diameter of the aperture. The cell is, however, virtually shortened 

 because of the waving movement of the tail. Taking into account the 



I SEC. 



Fig. 8. Record of the passage over the aperture of a rotating sperm 

 cell; the record can be divided into three parts, corresponding to the 

 movements of the head (H), middle piece (M), and tail (T) when pro- 

 jected on the aperture. 



