Page:Contraception; 1st ed. (IA in.ernet.dli.2015.94163).pdf/128

The object of the introduction of chemicals of any sort is the intention to incapacitate the spermatozoa and thus render them incapable of movement or of union with the ovum. The minute size and delicate structure of the spermatozoa render plasmolysis in vitro easy of achievement. As is well known, each human spermatozoon is 0.05 mm., or ⁠1/300⁠th of an inch, including its long. cilium or tail. (For descriptions of the spermatozoa of man and other animals, reference should be made to Marshall's excellent "Physiology of Reproduction."^[1]) In a normal ejaculate there are not only, as is so often stated, thousands of these, but millions; the ejaculate of a healthy man containing between one and six hundred million live, motile spermatozoa, the whole bulk of the ejaculate being as a rule 3 to 5 c.c. The quantity of plasmolysing chemical therefore required, although it has to deal with innumerable spermatozoa, is not great; and individual experience has shown that with the use of such a plasmolyser as quinine salicylate, a few grains is amply sufficient to leave a wide margin of safety. But, on the other hand, it is well known that