The Discovery of the “Semine Genitali Animalculis” Or Spermatozoa 93

The Discovery of the “Semine genitali Animalculis” or Spermatozoa 93

Chapter 6 The Discovery of the “Semine genitali Animalculis” or Spermatozoa

On 24 April 1674, Henry Oldenburg, the Secretary of the Royal Society, wrote to Van Leeuwenhoek, asking him to focus his microscope on human secretions such as sweat, saliva… and semen. Van Leeuwenhoek probably viewed the latter request with reluctance. Semen was a delicate subject in the strictly Protestant surroundings in which he lived. However, the respected gentlemen of the Royal Society were curious. They thought that microscopic examination of human semen might answer questions about reproduction that were intriguing many scholars in the 17th century: How did organisms reproduce and develop? At the time, this was known as the “question of generation”. Van Leeuwenhoek, one of their newest correspondents, felt that he could not refuse this request and investigated his own semen, carefully collected after conjugal intercourse (masturbation or “self-defilement” was regarded as a sin at the time). The result was not very impressive. Van Leeuwenhoek saw small, lifeless globules, but he did not attribute any special significance to them. As a subject for microscopic research, semen did not seem very interesting.

The Visit of Johan Ham

Three years later, in October 1677, an excited young man knocked on Van Leeuwenhoek’s door. Johan Ham was a 23-year-old student of philosophy in Leiden. It was not his first visit. On the recommendation of his uncle, Theodoor Craanen (Professor of Philosophy and Medicine in Leiden), he had admired a number of Van Leeuwenhoek’s specimens a few months earlier. Inspired by that visit, Ham had also begun to study samples under a microscope, including flies, lice, plants and much more. Now, however, he had made an extraordinary discovery. He had brought a phial containing a sample of ‘the spontaneously discharged semen of a man who had lain with an unclean woman’. This was

Figure 6.1 Theodoor Craanen, Johan Ham’s uncle

Figure 6.2 ‘The spontaneously discharged semen of a man who had lain with an unclean woman’ the semen of a man suffering from a venereal disease, probably gonorrhoea or syphilis, common complaints at the time. When Ham told him that ‘he had seen living animalcules in it, judging these animalcules to possess tails, and not to remain alive above twenty-four hours’, Van Leeuwenhoek immediately examined the sample and clearly saw the little