184 EDWIN J. CORN. 



IV. THE EFFECT OF THE CONCENTRATION OF THE SPERM SUS- 

 PENSION UPON THE ACTIVITY AND UPON THE 

 LONGEVITY OF SPERMATOZOA. 



The observations and the experiments that have been cited 

 show that sea urchin spermatozoa soon become inactive in a 

 certain concentration of hydrogen ions or of carbon dioxide. 

 In lower concentrations spermatozoa are the less active the 

 higher the concentration of hydrogen ions or of carbon dioxide 

 (see also Lillie, F. R., 1913). In the measurements of the carbon 

 dioxide concentration of sperm suspensions that have been re- 

 ported the sperm produced sufficient carbon dioxide in the more 

 concentrated suspension to inactivate themselves in about two 

 hours. The carbon dioxide production of inactive spermatozoa 

 is of course very much less than the carbon dioxide production 

 of highly active spermatozoa. Since spermatozoa are decreas- 

 ingly active the higher the concentration of carbon dioxide in the 

 suspension, the observed falling off with time of the carbon dioxide 

 production in all of the suspensions is easily understood. 



In very concentrated sperm suspensions, therefore, the sper- 

 matozoa are active for but a short time. That undiluted mam- 

 malian sperm exhibit but little activity was observed by Koel- 

 liker. He remarks: "In der Regel findet sich die Bewegung 

 allerdings nur am Rande des Tropfens, nicht weil hier eine Ver- 

 dunstung des Samens statt hat, . . . sondern weil am Rande 

 des Tropfens die Intercellular-flussigkeit in etwas bemerklicherer 

 Weise sich ansammelt" (Koelliker, A., 1856, p. 205). The ob- 

 servation has since been confirmed by many investigators and 

 for nearly all forms. The explanation of the activity of sperma- 

 tozoa at the border of the drop is contained in the observations 

 of Buller (Duller, A. H., 1902) and Lillie (Lillie, F. R., 1913) 

 quoted in the last section. At the edge of a sperm suspension 

 the oxygen concentration is higher and the carbon dioxide con- 

 centration lower than in any other part of the drop. Conse- 

 quently spermatozoa accumulate in the region of highest carbon 

 dioxide concentration. There they are very inactive, and live 

 for a very long time. 



Further evidence that the increased length of life in the more 

 concentrated suspensions is due to the decreased production of 



