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humours, chemistry, genetics, hereditary disease, medicine


The re-discovery of the works of Mendel and others has added greatly to our understanding of genetics. Such is now the case of Peter Severinus, with the recent recovery (or re-discovery) of his seminal work, Idea Medicinae Philosophicae (1571). Severinus concurred with Paracelsus’s (1493-1541) concept of seeds (little chemical factories) that worked on matter to form living things; but he was also aware of transplantation (grafting and cross-pollination) that changed phenotypes and genotypes in plants. Severinus applied this understanding to hereditary diseases in humans and extended Paracelsian theory. He believed that certain diseases in one’s offspring were caused by a parent’s infected (abnormal) seed. He observed that some hereditary diseases skip generations, and some eventually lose their force and die out. His understanding of hereditary diseases also gave hope for their treatment, i.e., the chemical imbalance associated with a hereditary disease could be altered with the proper chemical remedy. His theory of hereditary disease was discussed and respected for almost a century but, eventually, it was forgotten as medicine moved towards a mechanical view of biological processes, and focused on the matter theory, measurement, and eventually Lavoisier’s oxygen chemistry.