Abstract: A method of measuring sperm motility comprises directing a beam of light at an angle at less than 30.degree. into a thin film suspension of the sperm, and counting the number of reflections per unit time to provide an index of sperm motility. Apparatus for measuring sperm motility according to the above method comprises a holder including a pair of transparent plates beads for holding the sperm suspension in the form of a relatively thin film, means for directing the beam of light into the thin film suspension, an optical detector for detecting the reflection, and a counter for counting the number of reflections per unit time.

Abstract: Apparatus and method are described for using ultrasonic waves for removing microscopic particles from a liquid medium, such as algae from a solar or refuse pond, or blood cells from blood. The described apparatus includes an ultrasonic generator propagating ultrasonic waves of over one megacycle per second through the liquid medium to cause the flocculation of the microscopic particles at spaced points. In two described embodiments, the ultrasonic waves are propagated in the horizontal direction through the liquid medium, and baffle plates are disposed below the level of propagation of the ultrasonic waves. The baffles are oriented to provide a high resistance to the horizontal propagation therethrough of the ultrasonic waves and a low-resistance to the vertical settling therethrough of the flocculated particles.