154 The Theory of Atmospheric Germs. [April, 



Those who debate this question range themselves in two 

 classes, with defined lines of demarcation between them. 

 The ones say : living things do not necessarily arise from 

 pre-existing bodies, which possess or did possess attributes of 

 vitality ; but they may originate from non-living matter in 

 connection with the ordinary forces of nature. The others 

 say that living things invariably are the progeny of living 

 things ; that in nature only vital material is capable of 

 endowing non-vital matter with the special properties which 

 itself possesses. After a protracted debate in the learned 

 societies of France, the upholders of each side of the ques- 

 tion appear to have arrived at that stage at which each 

 prefers to remain unconvinced. More recently in this 

 country the ardour of debate has been displayed, and yet 

 there are strong forces in either camp. 



The following is a brief outline of the debateable ground. 

 It is well known that it is the tendency of moist organic 

 matter, under certain physical influences, to undergo certain 

 processes known as decay or decomposition. Either it dis- 

 integrates, evolving nauseous odours, and giving rise in the 

 course of the disintegration to a multiplicity of chemical 

 products organic or inorganic. Such is known by the term 

 putrefaction. Or, the organic material being less complex in 

 the beginning, the process runs a more definite course and 

 the products are less varied. Such is fermentation. 



In both instances there is observed intimately connected with 

 the process, the occurrence, growth, and multiplication of living 

 organisms, either amid the particles of the moist decompo- 

 sing substance or upon the surface, where these frequently 

 make their appearance as ordinary mildew. How are these 

 results explained by the two theories ? According to the 

 one, the molecules of a putrefying or a fermenting body are 

 in a state of motion, tending to the disruption of their 

 elements. The living particles observed are the results of 

 the communion of certain non-living elements with the 

 physical forces with which they are in relation. Thus there 

 is a strict analogy between crystallisation and creation. As 

 in the one case certain molecules under certain conditions 

 assume definite crystalline forms, "so certain molecules under 

 other certain conditions assume the appearances and the 

 attributes of vitality. 



According to the other theory, there is a single cause for 

 all the phenomena. This cause is the presence of living 

 matter. The organic elements of a putrescible or fer- 

 mentescible compound undergo disruption by no inherent 

 tendency of their particles to motion, but by the influence 



