SPONTANEOUS GENERATION. 933 



and vito-chemical forms of force working in the body, are entirely 

 unknown. Its truly marvellous results are considered in the following 

 Section on Reproduction Development. 



REPRODUCTION. 



Spontaneous Generation. 



The life of individual organism, whether vegetable or animal, is 

 limited, death, at last, ensuing from accident, disease, or natural 

 causes. The maintenance of the species, by the reproduction of new 

 individuals, is accomplished in different modes in different animals. 



All animals, so far as is known, even the very lowest, are produced 

 from parents. The occurrence of the original generation of an ani- 

 mal, without the intervention of a parent, or the so-called equivocal or 

 spontaneous generation, is not believed in by the best authorities. 

 All cases of supposed spontaneous generation, cited before the intro- 

 duction of good microscopes, may be set aside as valueless. The pres- 

 ent condition of the question is fully illustrated in the recent contro- 

 versy between MM. Pouchet and Pasteur. It is admitted by both 

 those observers, that only the lowest Protozoic forms of animal life 

 are concerned in this question, the assertions of Crosse and others, as 

 to the spontaneous development of a complete Annulose animal, being 

 unworthy of serious consideration. 



With regard to the Infusoria, however, it is alleged by Pouchet, 

 that, if impure water be boiled, so as to destroy all organic life in it, 

 and then be absolutely excluded from the air ; or if air only be ad- 

 mitted which has previously passed through red hot tubes ; or, again, 

 if water be boiled in flasks which are then hermetically sealed organ- 

 isms, belonging to the simplest forms of Infusorial life, will make their 

 appearance ; and that these will even be followed by the subsequent 

 appearance of higher ciliated Infusoria. It is strongly asserted that, 

 in such experiments, absolute care has been taken to prevent the acci- 

 dental intrusion of germs, however minute, into the water or air. By 

 Pasteur, on the other hand, it is affirmed that, if sufficient precaution 

 be taken, no manifestation of life occurs in the fluid experimented 

 upon, or at least, so exceptionally, that it may well be attributed to 

 the accidental entrance of floating germs. 



The following experiments have been devised by Pasteur, to illus- 

 trate this subject. Small flasks of boiled water have been closely 

 fitted at the mouth with tubes, into a bend or bulb of which cotton- 

 wool is introduced; this intercepts floating germs, but yet allows the 

 interchanges proper to gaseous diffusion : in such experiments, no 

 organisms are developed in the water. On the other hand, with the 

 same fluid boiled, and placed in a flask, fitted with a similar tube with- 

 out the cotton-wool, multitudes of Infusoria are developed. In other 

 experiments, instead of cotton-wool, gun-cotton was employed, and 



