Male Reproductive Function and the Composition of Semen: General Considerations

Abstract

The modern era of the physiology of reproduction in the male is commonly, and rightly so, accepted as having been ushered in by Leeuwenhoek’s sensational letter to the Royal Society, dated November 1677, reporting the first-ever demonstration in semen of motile spermatozoa. From another of his famous communications, cited above and submitted 8 years later, it is evident that Leeuwenhoek intuitively associated the existence of spermatozoa with male fertilizing ability, by recognizing that even though a man may be keenly interested in the opposite sex, this alone is not enough to guarantee the birth of offspring. He anticipated, moreover, yet another basic concept of male reproductive biology, by proclaiming that for the act of procreation to be fulfilled, the spermatozoa, as well as being motile, must also be sufficiently energetic to survive in the female tract for a certain period, presumably to attain their full potential. The precise duration of that critical timespan he was, of course, unable to back up with experimental evidence.

“Now, when a man is unable to beget children by his wife, although his virility is unimpaired, he is said in common parlance to have a cold nature. To my mind, however, it would be more apt to say that no living animalcules will be found in the seed of such a man, or that, should any living animalcules be found in it, they are too weakly to survive long enough in the womb.” Antoni van Leeuwenhoek 1685