91 



that inorganic matter does not contain *' the promise and 

 potency of all terrestial life"; indeed this is the doctrine 

 enunciated by Tyndall himself at Belfast ; and it is equally 

 certain that even many of those who do deny that orgatj - 

 isms capable of reproducing their species are ever evolved 

 from absolutely unorganised matter, nevertheless do not 

 consider the presence of any specific atmospheric or other 

 germ as necessary for the reproduction of any given species. 

 There is a domain which still invites the experimentalist, 

 who may succeed in harmonising apparently antagonistic 

 ideas. A very large and important amount of work has 

 been done in showing the analogies between fermentation 

 and disease, and in discovering apparently specific patho- 

 genic microbes or ferments. Indeed, in recent years the 

 multiplication of specific microbes has become almost em- 

 barrassing. But though strong evidence has unquestionably 

 been adduced tliat, at least in certain cases, the characteris- 

 tic microbe is the originator of the disease, or is capable 

 of conveying it, the very multiplication of microbes is 

 reviving the question as to whether these organisms 

 are the causes or merely the accompaniments (in the sense 

 in which the vulture is the accompaniment of carrion), or 

 even the products of disease. The recognition of these facts 

 does not imply any depreciation of the practical value 

 or the significance of the work which has been done during 

 the last thirty years, but helps us to a clearer view of its 

 bearing and scope. 



4. — In considering the development of the germ theory we 

 may pass almost directly from Leeuwen-hoek and his con- 

 temporaries to Pasteur, As a matter of history we must 

 not ol course overlook the observations of Cagniard La Tour 

 and Schwann, based upon an observation of Leeuwenhoek, 

 and really establishing the vegetable nature of yeast. But 

 it is to Pasteur that we are indebted for definite progress in 

 establishing or refuting the ideas which sprang immediately 



