82 



Oxford, and those reported in this communication, are suffi- 

 cient answer to the criticisms of M. Edwards." Then as to 

 his thoroughness : — most persons would have rested on the 

 results of his thirty-three well-devised experiments, proving 

 " that the boiled solutions of organic matter made use of 

 exposed only to air which has passed through tubes heated 

 to redness, became the seat of infusorial life ;" but all would 

 not have concluded that, after all, they " throw but little 

 light on the immediate source from which the organisms have 

 been derived," nor would many have closed an impartial 

 summary of the opposing views in this judicial way: — 



" If, on the one hand, it is urged that all organisms, in so 

 far as the early history of them is known, are derived from 

 ova, and therefore from analogy we must ascribe a similar 

 origin to these minute beings the early history of which we 

 do not know, it may be Urged with equal force, on the other 

 hand, that all ova and spores, in so far as we know anything 

 about them, are destroyed by prolonged boiling; therefore 

 from analogy we are equally bound to infer that Vibrios, 

 Bacterians, etc., could not have been derived from ova, since 

 these would all have been destroyed by the conditions to 

 which they have been subjected. The argument from anal- 

 ogy is as strong in the one case as in the other." 



Returning to the subject again a few years later, with a 

 critical series of twenty experiments, each of three, five, ten, 

 fifteen, or even twenty flasks, used byway of checks and com- 

 parisons, — a rigorous experimenter would have been satisfied 

 when he had proved that sealed solutions subjected to a heat 

 of at least 212° for from one to four hours, became the seat 

 of infusorial life, at least of such as Vibrios, Bacterians and 

 Monads, while all infusoria having the faculty of locomotion 



