20 DEVELOPMENT OF THE GERM THEORY. 



imply a sudden breach of continuity such as we find in no other 

 part of the scale of animal life, and be contrary to the opinion of 

 Locke, " that in all the corporeal world we see no chasms or gaps." 



Admitting, however, that even if we never reach actual proofs 

 of the existence of these minute forms of life, be they insect or of 

 other kind, he argues that the probability of their existence is 

 little lessened by the failure, considering the obstacles which have 

 to be surmounted. And, if existing, we may presume that they 

 have many points of affinity with well-known insect genera, such 

 as sudden generation at irregular and often distant periods under 

 certain conditions of season or locality, and the diffusion of the 

 swarms so generated over wide tracts of country often following 

 particular lines of movement. Whatever is true or peculiar to the 

 habits of insects, or the forms of animalcule life, obvious to our 

 senses, is likely to be equally applicable to those whose minuteness 

 removes them further from our observation. Their generation 

 may be presumed to be even more dependent on casualties of 

 season or place, their movements determined by causes of which 

 we .are less cognizant, and their power of morbidly affecting the 

 body, to be in some proportion to their multitude and minuteness. 



Claiming that these considerations are of great interest to the 

 general theory of disease, he says they have close reference to 

 contagious exanthemata in particular ; and though not sanctioned 

 by any direct proofs in relation to these diseases, yet fully justify 

 the prosecution of the research through every possible channel 

 and render plausible, at least, the arguments of those who have 

 ventured to support the opinion that they depend upon the action 

 and phenomena of parasitic life. 



Having regarded the question as to whether the epidemic ten- 

 dency of carbuncular boils has not depended on causes from 

 without, giving hydrophobia and glanders as instances of disease 

 conveyed from animals to man ; noting that epidemic influenzas 

 are in no way produced by atmospheric states or changes, he then 

 takes up the subject of cholera, and proceeds in the most masterly 

 manner to elucidate his theory by the remarkable phenomena 

 shown in this disease. 



After tracing the history of its diffusion for twenty years under 

 every climate, in every place, the disease being always absolutely 



