Studies in the Physiology of Spermatozoa

The total available energy of spermatozoa, as measured by total carbon dioxide production, is a constant. 2. The rate at which the total available energy is expended is a function of the activity and an inverse function of the length of life of spermatozoa. 3. The activity and the length of life of spermatozoa is a function of the temperature, and of the hydrogen ion concentration of the suspension. Up to a certain point decreasing the temperature or increasing the hydrogen ion concentration decreases the activity and increases the length of life of spermatozoa. Lower temperatures or greater acidities destroy spermatozoa, and the more so the longer they are subjected to these abnormal media. Conversely, within limits, decreasing the hydrogen ion concentration or increasing the temperature increases the activity and decreases the length of life of spermatozoa. Further increase in temperature or in alkalinity irreversibly agglutinates spermatozoa. 4. The ability of spermatozoa to fertilize eggs of the same species is a function of their activity (as measured by their carbon dioxide production, or its converse, their length of life). Spermatozoa lose their power to fertilize as a function of the time of insemination, and of the dilution and of the hydrogen ion concentration of the suspension. If spermatozoa that have been in the suspension for but a short time are added to eggs in a large volume of sea water a decrease in the hydrogen ion concentration of the sperm suspension (that is, an increase in the alkalinity) increases the activity and the fertilizing power of the spermatozoa. Such spermatozoa will, however, lose their power to fertilize when transferred to ripe eggs in sea water long before spermatozoa that have been relatively inactive in more acid sperm suspensions. 5. If spermatozoa that have been at the same hydrogen ion concentration are added to eggs in sea water at the same time, increasing the concentration of spermatozoa increases the percentage of eggs that are fertilized. This may be explained either by assuming that in the greater concentration more spermatozoa will on the average arrive at the periphery of the egg with sufficient action (having the dimensions of energy x time) to initiate development, or by assuming that mass action of spermatozoa may be effective in initiating the development of the sea urchin egg. The latter explanation has been suggested by Glaser, who pointed out that the further assumption that more than one spermatozoön was necessary "to carry out the bi-parental effect" was not involved. 6. Increasing the carbon dioxide concentration increases the hydrogen ion concentration of the suspension, decreases the activity of spermatozoa and increases the length of their life. Sea water of the optimum carbon dioxide concentration for increasing the length of life of spermatozoa is also of the optimum hydrogen ion concentration. It is possible, however, that carbon dioxide affects the physiological condition of spermatozoa otherwise than by means of ionized hydrogen. 7. That decreasing the oxygen concentration of sea water or decreasing the oxidations of spermatozoa by adding KCN to sea water increases the length of their life has been reported by Drzewina and Bohn. Experiments confirming their results and demonstrating that under such conditions sperm are relatively inactive are reported. 8. Spermatozoa increase the carbon dioxide and, therefore, the hydrogen ion concentration of concentrated sperm suspensions to the optimum for decreasing their own activity in a very short time. In such suspensions sperm live for a very long time. McClendon has recently estimated that respiration in sea water that raises the carbon dioxide and the hydrogen ion to a concentration approximately equal to that which is most effective in prolonging the life of a sperm suspension, uses up all of the available oxygen. It is therefore suggested that high carbon dioxide and hydrogen ion concentration and low oxygen concentration are the environmental conditions that obtain in a concentrated sperm suspension. These conditions approximate those of ripe sperm in the testes very much more closely than they do those of sperm that are shed in the ocean. 9. The addition of beef broth to sea water increases the length of life of the spermatozoa. Gemmill suggested that beef broth furnished "artificial nutrition." It is pointed out that the addition of beef broth to sea water increases the hydrogen ion concentration and decreases the activity of spermatozoa. 10. Sea water that has contained the eggs of the sea urchin, Arbacia, tremendously activates spermatozoa. It may be that the fertilizing power of spermatozoa that are added to eggs in sea water during this period of activation is increased in much the same way that the fertilizing power of spermatozoa is increased for a short period of time by decreasing the hydrogen ion concentration (increasing the alkalinity) of sea water. Subsequent to the period of activation spermatozoa become inactive in egg water. Such egg water has a high hydrogen ion concentration. This is reached as a result either of the carbon dioxide produced by eggs and eliminated into the sea water, or by spermatozoa during the period of their greatest activity. If spermatozoa are added after they have become inactive, the percentage of eggs that are fertilized depends upon the degree of inactivity and the degree of reactivation (such as is brought about by transferring spermatozoa to sea water without high hydrogen ion or carbon dioxide concentration) which the experimental conditions afford. The sooner spermatozoa become inactive and the more completely inactive they become, the longer their life. The hydrogen ion concentration of egg water that is most effective in preserving the life of spermatozoa is precisely that of acidified sea water that best subserves the same function. Other effects of egg water upon the physiological condition of spermatozoa have not been considered in this investigation.