The chemical composition of the pre-sperm fraction of bull ejaculate obtained by electrical stimulation

Semen was collected from bulls by means of the electro-ejaculation method developed by Thibault et al. (1948). 2. A copious sperm-free fraction of the ejaculate, produced in the early phase of stimulation, was examined for its chemical composition. 3. This secretion was found to have a low protein content, but its chloride concentration was higher than in the sperm-containing fractions of the ejaculate. Fructose and citric acid occurred in very low concentrations, and 5-nucleotidase was absent in the pre-sperm secretion. This indicates clearly that the secretion does not originate either in the seminal vesicles or in the ampullar glands; it is probable that it represents a discharge from the urethral glands. 4. The effect of the pre-sperm ejaculate fraction upon bull sperm fructolysis and motility was examined; both were unaffected by a considerable excess of this secretion. 5. The chemical composition of the pre-sperm secretion makes it unlikely that under physiological conditions it could play a role in the nutrition of the spermatozoa; presumably, its chief function is the clearing of the urethral passage prior to the descent of the semen proper.