Looking down on sperm motion： a useful addeddimension？

The assumed association of sperm motility with fertility has long beena preoccupation of clinicians. Whereas assessing fertility of a couple has relatively easy end-points （time to pregnancy, number of children）, assessing motility does not. ＂[he many methods developed to determine it include assessing a sperm population subjectively （by grading） and objectively （by measuring its motion-induced movement into a light beam by spectrophotometry or nephelometry）, and making measurements on individual sperm cells （by stroboscopic or multiple-exposure photography or digitized video-recordings）.