i62 Appendix. 



lows that it must be either a colloid or solid matter. Next in 

 point of order Drs. Schroeder and Von Dusch* helped clear up 

 up this point by showing that the simple exclusion of air from an 

 infusion by a plug of cotton wool prevented both fermentation 

 and development of organisms ; and finally Tyndall settled the 

 matter definitely by showing that ordinary air is full of solid 

 'particles of matter, and that they are entirely strained out by 

 filtration through the plug of wool. It only remains, therefore, 

 to prove that among these particles are germs which, under ap- 

 propriate conditions, are capable of being developed into animal 

 life. " This," says Huxley, " was done by M. Pasteur, in those 

 beautiful researches^ which will ever render his name famous, 

 and which, in spite of all attacks upon them, appear to me to be 

 models of accurate experimentation and logical reasoning." In 

 point of time, however, this demonstration was not made until 

 the third or last epoch in the history of spontaneous generation. 



yi Epoch. This dates from the year 1858, when the ques- 

 tion — which by general consent had been considered as closed — 

 was reopened Paris by Pouchet, the distinguished naturalist of 

 Rouen. He sent a communication to the French Academy in 

 which he declared that lie had experimentally proven the truth 

 of spontaneous generation, and in the following year he pub- 

 lished his well-known work on the subject. j It may be well to 

 note just here, as bearing upon the reliability of his evidence and 

 arguments, that he was undoubtedly influenced by a motive, for 

 in a preface by him to Pennetier's work on the origin of life, he 

 says: "For all reflecting minds heterogenous production is a 

 logical consequence of the appearance and ascending develop- 

 ment of organized beings upon the globe. "§ Furthermore, in 

 the very opening paragraph of the preface to his own book, he 

 uses this expression : " When by meditation it was evident to me 

 that spontaneous generation was one of the means employed by 



* Annal. de Chimie, tome XLI., 185il, and Chemical News, Vol. V., 1862. 



t Prof. Tyndall, somewhat enthusiastically says, that his " labors in 

 connexion with this subject may lie fitly called immortal."— itoiert, Februa- 

 ry 12, 1876, p. 262. 



X Helerof/enie ; on Traite de la (leneration spontanec, base siir des youvelle.s 

 Experiences. Paris, 18.59. 



? Quoted by Dalton, loe. eit. 



