Page:Contraception; 1st ed. (IA in.ernet.dli.2015.94163).pdf/129

results obtained in vitro are often dissimilar from those obtained in vivo, and I am much inclined to think that the reason that the quinine plasmolyser, for instance, is so much more reliable when applied in the medium of grease (such as low melting-point cocoa butter or oil), than when applied in other ways, is due to the additional physical effect of the grease itself which acts as a clog to the movements of the spermatozoa. I have heard it said in discussion that quinine pessaries with the quinine left out are quite as effective as those containing it, but I do not entirely assent to this.

The number of chemicals in general use is curiously restricted. The reason for this does not seem to have any real scientific basis, but to depend on the fact that hitherto knowledge on the whole subject of contraception has largely been left in the hands of the unscientific commercial retailer, even of the hanger-on of vice. Such persons are profoundly ignorant of the scientific basis for any procedure they may advocate, and therefore the few substances which long ago became known have tended still to be used to the exclusion of a larger number of other substances theoretically of equal value, which might have been used, or whose advantage might have been discovered had the subject