SPONTANEOUS GENERATION. 



437 



contains some germs of living organisms, but 

 that what proportion these bear to the much 

 more bulky, and probably more numerous, or- 

 ganic particles and fragments resulting from the 

 breaking up of previous living matter of various 

 kinds, is uncertain. It has been also generally 

 admitted that any living organisms or germs 

 which chanced to fall from the air into suitable 

 fluids would initiate fermentation or putrefac- 

 tion therein. The question really requiring to be 

 solved has always been (though it has not been 

 uniformly recognized) whether mere organic de- 

 bris from the air, either in the form of particles 

 or of larger fragments, could or could not also 

 bring about such changes in suitable fluids. 



The legitimacy of this doubt is perfectly ob- 

 vious. The doctrine of fermentation generally 

 adopted anterior to that of M. Pasteur was the 

 one promulgated by Baron Liebig. This latter 

 has been known as the physical or the chemico- 

 physical theory, in contradistinction to that of M. 

 Pasteur, which is commonly spoken of as the 

 germ-theory, or the vital theory of fermentation. 

 Now, according to the original doctrine of Lie- 

 big, a ferment was a portion of organic matter 

 in a state of motor-decay. The molecular move- 

 ments communicated to a suitable liquid by such 

 changing organic matter were supposed by him 

 to be capable of initiating fermentative changes. 

 In short, Liebig attributed to decaying organic 

 matter just such functions as Pasteur has striven 

 to concede only to living units or organisms. 



It is Liebig's doctrine, therefore, which legiti- 

 mately suggests the doubt above mentioned in 

 regard to the possible potencies of atmospheric 

 particles other than actual germs. It was his 

 view which from the first made it desirable that 

 absolute proof should be looked for from the 

 germ- theorists before their doctrine was ac- 

 cepted, and before effects referable, it is true, to 

 the influence of atmospheric dust are declared not 

 to be in part accounted for by the fermentative 

 agency of some of the dead organic particles and 

 fragments with which the air is known to teem. 



This is a view which is not peculiar to myself. 

 It is, and has long been, held by others, in proof 

 of which I need only quote the following brief 

 passage from the writings of another celebrated 

 German chemist. Speaking of experiments which 

 had been made with suitable boiled fluids, ex- 

 posed first of all to air which had been either 

 calcined or filtered, and then to ordinary air, 

 Prof. Gerhardt (" Chimie Organique," t. iv., p. 

 545) says by way of comment upon the conclu- 

 sions drawn from them by the germ-theorists : 



" Si dans les premieres experiences l'air calcine" 

 ou tamise s'est montre" beaucoup moins actif que 

 l'air non sounds a ce traitement, c'est que la cha- 

 leur rouge ou le tamisage enleve a l'air non-seule- 

 ment les germes des infusoires et des moisissures, 

 mais encore les debris des matieres en decompo- 

 sition qui y sont suspendues, c'est-a-dire les fer- 

 ments dont l'activite" viendrait s'ajouter a eelle de 

 l'oxygene de l'air." 



All this seems to me perfectly plain, yet Prof. 

 Tyndall is pleased to find fault in the last number 

 of this Review, because, as he says, the name of 

 Baron Liebig has been unwarrantably or need- 

 lessly introduced into these discussions. He fur- 

 ther accuses me of speaking in "vague" terms, 

 because I have not quoted Baron Liebig for more 

 than that to which he has given his testimony. 



The correlation of organisms with the major- 

 ity of fermentations is now freely admitted on all 

 sides. But it was not a fact so well known to 

 Liebig when he originally published his doctrine 

 as to the causes of fermentation. Baron Liebig 

 lived, however, into the time when the fact of 

 this correlation was generally known and ad- 

 mitted, and he saw nothing therein to make him 

 renounce his previous views. On the contrary, 

 he slightly widened them after the correlation of 

 organisms with fermentations had become estab- 

 lished, and endeavored to show that the admitted 

 actions of living units in initiating fermentations 

 were but other exemplifications of his general 

 doctrine, that fermentations are induced by cer- 

 tain communicated molecular movements, some- 

 times emanating from organic matter in a state 

 of decay, and sometimes resulting from the vital 

 processes of living units. 



I quite agree with Prof. Tyndall in thinking 

 that Liebig's was a truly scientific doctrine, 

 founded, as the former tells us, on " profound 

 conceptions of molecular instability." 



If, then, as Liebig contended, organic matter 

 in a state of decay is capable of acting as a fer- 

 ment, and of initiating the common fermentations 

 and putrefactions, there surely can be no error in 

 quoting him in support of such views. And if it 

 has also been shown that the appearance and in- 

 crease of the lowest living particles are always a 

 correlative of these processes, Liebig's view, if it 

 is true at all, must be true for the whole of the 

 processes which are essentially included under 

 the term fermentation. 



The heterogenist has, therefore, perfectly good 

 ground for demanding proofs of error from the 

 germ-theorist rather than more or less probable 

 guesses based solely upon the germ-theorist's 



