cxx THE BEGINNINGS OF LIFE. 



certain diseases, and especially some of epidemic and con- 

 tagious kind, are derived from minute forms of animal life, 

 existing in the atmosphere under particular circumstances, 

 and capable by application to the lining membranes, or other 

 parts, of acting as a virus on the human body.' Now, the 

 fact of the multiplication of the virus within the body was 

 the peculiarity of these diseases which, above all others, 

 caused such an hypothesis to be received with favour. 

 Causes which are specific and which seem capable of self- 

 multiplication what can such agents be but living things 

 of some kind, plant or animal? This mode of argument 

 was, with many, all powerful. And when, after the discovery 

 of the yeast-plant by Schwann, in 1836, new doctrines con- 

 cerning fermentation began to prevail, the views of those 

 who believed in the living nature of the specific causes of 

 epidemic diseases were in part strengthened. If all fer- 

 mentations were initiated by the agency of living organisms, 

 and the specific diseases were comparable to processes of 

 fermentation, then, how natural was it that many who were 

 moreover influenced by the other analogies, should be led 

 to imagine that the actual causes of these diseases were 

 also living organisms ? Only now, attention became directed 

 to the much lower organisms which are so frequently asso- 

 ciated with fermentative and putrefactive changes, instead of 

 to insects ' minute beyond the reach of all sense/ 



Here then is the origin of what in modern times has been 

 termed * The Germ-Theory of Disease.' Like homoeopathy 

 and phrenology, this theory carried with it a kind of 

 simplicity and attractiveness, which insured its acceptability 

 to the minds of many. Now, however, it seems to rest upon 

 foundations only a little more worthy of consideration than 

 those upon which these other theories are based. But, 

 owing to its influence, in combination with the more gene- 

 rally received doctrines concerning the origin of life, there 



