A New Method of Measuring the Activity of Spermatozoa

Abstract

1. A new and quantitative method of estimating the average speed of a suspension of spermatozoa has been developed. The method, in which the phenomenon known as probability-after-effect and kinetic theory principles are made use of, can be applied to any system of organisms which move in random directions, in one, two or three dimensions. 2. The experimental procedure is to place a drop of sperm suspension on a microscope slide with a cover-slip on top of the drop, and photograph the spermatozoa at known time intervals. 3. The number of spermatozoa in a region of known size is counted on each photograph. The estimated mean or average speed of the sperm suspension, c is given by the equation c = -(Φr/2τ)loge{I - σ2/2n}, where r is the radius of a circular region in which the number of spermatozoa is counted, τ is the time interval between photographs, σ2 is the average of the square of the differences between the numbers of spermatozoa counted on consecutive photographs, and nis the average number of spermatozoa in the circular region. 4. Appropriate formulae for non-circular regions and for the precision of estimates of care given. 5. A method of testing whether the directions of movement of spermatozoa are random has been applied to bull semen diluted I/4 with phosphate buffer containing fructose. The movements were found to be random. 6. The distribution of sperm speeds was determined and found to be somewhat skew and leptokurtic, with mean 123 µ/sec and standard deviation 39 If dead or motionless spermatozoa were included, the mean speed became 117 µ/sec. 7. Using the probability-after-effect equation given in (3), the mean speed of the suspension, including dead or motionless spermatozoa, was found to be III µ/sec., with a standard error of 24.5. The standard error and therefore the precision of the estimate is under the control of the experimenter. 8. Practical instructions for carrying out measurements are summarized in a separate section.