chap, ii SPONTANEOUS GENERATION 43 



contemporary, in the latter half of the seventeenth century 

 adduced strong reasons for ascribing the origin of the organisms 

 of putrefaction to invisible air-borne eggs. L. Joblot and H. 

 Baker in the succeeding half-century investigated the matter, and 

 showed that putrefaction was no necessary antecedent of the 

 appearance of these beings : that, as well as being air-borne, the 

 germs might sometimes have adhered to the materials used for 

 making the infusion ; and that no organisms were found if the 

 infusions were boiled long enough, and corked when still boiling. 

 These views were strenuously opposed by Needham in England, by 

 Wrisberg in Germany, and by Buffon, the great French naturalist 

 and philosopher, whose genius, unballasted by an adequate know- 

 ledge of facts, often played him sad tricks. Spallanzani made a 

 detailed study of what we should now term the " bionomical " or 

 " oecological " conditions of Protistic life and reproduction in a 

 manner w T orthy of modern scientific research, and not attained by 

 some who took the opposite side within living recollection. He 

 showed that infusions kept sufficiently long at the boiling-point 

 in hermetically sealed vessels developed no Protistic life. As he 

 had shown that active Protists are killed at much lower 

 temperatures, he inferred that the germs must have much higher 

 powers of resistance ; and, by modifying the details of his experi- 

 ments, he was able to meet various objections of Needham. 



Despite this good work, the advocates of spontaneous genera- 

 tion were never really silenced ; and the widespread belief in the 

 inconstancy of species in Protista added a certain amount of 

 credibility to their cause. In 1845 Pineau put forward these 

 views most strongly; and from 1858 to 1864 they were 

 supported by the elder Pouchet. Louis Pasteur, who began 

 life as a chemist, was led from a study of alcoholic fermentation 

 to that of the organisms of fermentation and of putrefaction and 

 disease. He showed that in infusions boiled sufficiently long 

 and sealed while boiling, or kept at the boiling-point in a sealed 

 vessel, no life manifested itself: objections raised on the score of 

 the lack of access of fresh air were met by the arrangement,. so 

 commonly used in " pure cultures " at the present day, of a flask 

 with a tube attached plugged with a little cotton-wool, or even 

 merely bent repeatedly into a zigzag. The former attachment 

 filtered off all germs or floating solid particles from the air, the 

 latter brought about the settling of such particles in the elbows 



