142 Cells; or, Evolution, 



eden, Pasteur, Tyndall. It consisted in precluding 

 all possibility of live germs penetrating into a given 

 medium: the medium contained some dead organic 

 matter, in which such germs or embryos of animal- 

 cular, bacterial or microbic life, as you choose to call 

 it, are known to grow: then it was kept under 

 strict examination, to observe whether, these con- 

 ditions being rigidly kept, any life appeared in the 

 dead material. Notice then the conditions of the 

 problem: a solution, called proteinaceous, is pro- 

 vided,-one capable of the highest putrescence, and 

 therefore prime material for putrefactive germs to 

 settle on and develop in; but the solution is abso- 

 lutely sterilized, that is, cleansed of every particle 

 which can possibly be a germ of life; and it is 

 placed in an optically pure, or absolutely calcined, 

 air. Now, the conclusion ascertained is this: while 

 such conditions are maintained, no matter what 

 length of time may be suffered to elapse, that pu- 

 trescible fluid will remain absolutely without trace 

 of decay. There is no putrefactive life in it, no 

 microbes, no bacteria, simply because there is no 

 antecedent parental life there to produce them. 

 Such is the exclusive, the negative way of proving 

 that life can come only from life. Omne vivum 

 ex vivo. 



157. There remains the positive system, which 

 will take tip the direct study of these animalcules, 

 and will tell us how each has come into being, upon 

 Its being found to develop in any given medium. 



