[Original procreation or generational change? The investigation of cysticercus and tapeworms]

The doctrine of the abiogenesis postulated the origin of human and animal intestinal worms from "not complete digested ingesta". Indeed Peter Simon Pallas (1741-1811) defined already 1760 in his dissertation that endoparasitic worms reproduce themselves by eggs. But he characterised the nature of cysticercus as "pathologically degenerated tail bladder". In 1856 Rudolf Leuckart (1822-1898) paraphrased the alternation of generation with "marvellous metamorphoses and peculiar form of development". The Dane Johannes Japetus Smith Steenstrup (1813-1897) recognised finally the principle of the alternation of generation and Gottlob Friedrich Heinrich Küchenmeister (1821-1890), a physician at the Saxon city Zittau realised the special correlation between the alternate and end host of tapeworms. Both, Leuckart and Küchenmeister proved their insights by animal and human experimentations.