SECT. 3] AND EIGHTEENTH CENTURIES 169 



some and has been able to see the heart formed in them and beating, 

 together with some of the arteries" (Blampignon). 



Swammerdam's support for preformation came from a different 

 angle. He had been investigating insect metamorphosis, and, having 

 hardened the chrysalis with alcohol, had seen the butterfly folded 

 up and perfectly formed within the cocoon. He concluded that the 

 butterfly had been hidden or masked {larvatus) in the caterpillar, and 

 thence it was no great step to regard the Qgg in a similar light. Each 

 butterfly in each cocoon must contain eggs within it which in their 

 turn must contain butterflies which in their turn must contain eggs, 

 and so on. Before long, Swammerdam extended this theory to man. 

 "In nature", he said, "there is no generation but only propagation, 

 the growth of parts. Thus original sin is explained, for all men were 

 contained in the organs of Adam and of Eve. When their stock of 

 eggs is finished, the human race will cease to be." 



In 1684 Zypaeus reported that he had seen minute embryos in 

 unfertilised eggs, and there were other similar claims. ''^Hinc recentiores 

 physiologV\ said Schurigius in 1732, ^^ hominem in ovulis delineatum 

 quoad omnes partes in exiguis staminibus ante conceptionem existere 

 statuunt" 



Swammerdam cannot be regarded simply as one of the principal 

 pillars of the preformation theory. His own embryological researches, 

 which were made chiefly on the frog, were remarkable in many 

 ways. He was the first to see and describe the cleavage of the egg- 

 cell and later segmentation. He said that there was a time during the 

 development of the tadpole when its body consisted of granules 

 {greynkens or klootkens), but as these grew smaller and much more 

 numerous they escaped his penetration. Leeuwenhoek also saw these 

 cells, and his account was published long before Swammerdam's, 

 but his observations on the rotating embryos oi Anodon and the eggs 

 of fleas were equally interesting. 



3-8. Robert Boyle and John Mayow 



In 1674 John Mayow, a young Oxford physician, published his 

 tractate, De Respiratione Foetus in Utero et Ovo, which was included as 

 one of the parts of his Tractatus Quinque medico-physici in that year. 

 Mayow was the first worker to realise that gaseous oxygen, or, as he 

 termed it, the " nitro-aerial " vapour, was the essential factor in the 

 burning of a candle and the respiration of a living animal. His work 



