1. The mean velocity ῡ and the velocity frequency distribution f(υ) of bull spermatozoa with normal motility have been determined in standardized eggyolk—citrate buffers at different pH values, ranging frompH 5·70 to 8·35.Under assumed approximately anaerobic conditions at37·0 ± 0·1° C. the mean velocity was found to show a straight-line relationship -with pH in the physiological region pH 5·70–7·50, according to the general equationStatistically, k was shown to be a linear function of a, namely,Consequently, the dependence of the mean velocity of the spermatozoa from any ejaculate can be characterized by the one parameter a = dῡ/dpH. (dimension μ/sec./pH), determining the slope of the ῡ υs. pH curve.The mean velocity of all individual spermatozoa (measurements of all ejaculates at the same pH value pooled together) could be described accurately by the equation:For some ejaculates the linear relationship was found to hold up to pH 8·00.2. The velocity frequency distribution curves were found to change with pH. At pH 5·70 the curves are skew with a relatively high top value. At increasing pH values both the top value and skewness decrease. The mean standard deviation of the velocity distribution f(υ) was found to be proportional to pH and could be described by the equationThis means that the variability in swimming speeds of the individual spermatozoa of any ejaculate increases proportionally with pH, indicating a strain effect of increasing alkalinity on the population, irrespective of the general stimulation of motility in the region up to pH 7·50.3. At each pH value the mean velocity decreases with time. Under assumed approximately anaerobic conditions at 37° C. the speed of velocity decrease as a function of pH was found to differ so much between different ejaculates that no generalization could be derived from the available material. The same holds for the effect of pH on the number of normally moving spermatozoa in the diluted ejaculate.4. The total number of spermatozoa moving normally depends on pH, but the optimum varies with the individual ejaculates.

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A kinetic theory is derived for the relationship between numbers of spermatozoa, sperm movement, and the probability of fertilization. The theory shows good agreement with experimental results. Cf. A.B.A., 33, Nos. 1872 and 1873. F. S. (Abstract retrieved from CAB Abstracts by CABI’s permission)