?7 8 BIOLOGY AND ITS MAKERS 



and toads and other animals arose from the mud of ponds 

 and streams through the vivifying action of the sun's rays. 

 Rats were supposed to come from the river Nile, the dew was 

 supposed to give origin to insects, etc. 



The scientific writers of this period had little openness of 

 mind, and they indulged in scornful and sarcastic comments 

 at the expense of those who doubted the occurrence of 

 spontaneous generation. In the seventeenth century Alex- 

 ander Ross, commenting on Sir Thomas Brown's doubt as 

 to whether mice may be bred by putrefaction, flays his an- 

 tagonist in the following words: "So may we doubt whether 

 in cheese and timber worms are generated, or if beetles and 

 wasps in cow-dung, or if butterflies, locusts, shell-fish, snails, 

 eels, and such life be procreated of putrefied matter, which 

 is to receive the form of that creature to which it is by 

 formative power disposed. To question this is to question 

 reason, sense, and experience. If he doubts this, let him go 

 to Egypt, and there he will find the fields swarming with 

 mice begot of the mud of Nylus, to the great calamity of 

 the inhabitants." 



II. From Redi to Schwann. — The second period em- 

 braces the experimental tests of Redi (1668), Spallanzani 

 (1775), and Schwann (1837) — notable achievements that 

 resulted in a verdict for the adherents to the doctrine of 

 biogenesis. Here the question might have rested had it 

 not been opened upon theoretical ground by Pouchet in 

 1859. 



The First Experiments. — The belief in spontaneous gen- 

 eration, which was so firmly implanted in the minds of natu- 

 ralists, was subjected to an experimental test in 1668 by the 

 Italian Redi. It is a curious circumstance, but one that 

 throws great light upon the condition of intellectual develop- 

 ment of the period, that no one previous to Redi had at- 

 tempted to test the truth or falsity of the theory of spon- 



