35 



but the fact will help us to understand that cells may be 

 developed by these micro-organisms capable of producing very 

 diverse effects upon the system ; and I incline therefore to the 

 view that, probably from the simple neglect of ordinary sanitary 

 measures, innocuous micro-organisms may become virulent and 

 that diseases may arise de novo. 



I have however detained you already too long with these 

 speculations, and will not proceed further with them, tempting 

 and important though the subject may be. One thing is clear 

 and certain ; there is very distinct evidence showing a relation 

 between bacteria and certain diseases both in man and animals ; 

 but what the exact modus operandi is in the production of the 

 disease can only be learned from further investigation, and 

 additional study may throw a very different light on the relation- 

 ship of these organisms to the respective maladies from that 

 in which it may now be regarded. Whether this will be 

 so or not, it seems to me, that with increasing knowledge of 

 the chemical changes in the blood and in the tissues, we are 

 on the threshold of most important discoveries, and of a 

 very marked advance in the science of medicine. That physio- 

 logists are recognising in a greater degree than formerly the impor- 

 tance — nay, the absolute necessity — of further acquaintance with 

 chemical physiology, is shown in a marked way, by the appear- 

 ance of such works as those of Gamgee and Charles, and especially 

 that most recent and most valuable one of M^Kendrick. Perhaps 

 by further investigations into the chemical changes produced by 

 bacilli, the constitution of the proteid molecule, complex as its 

 nature is now regarded, may be unravelled and its properties 

 better understood ; we may be able to discover, possibly, what 

 poison it is which the bacilhis secretes, or how it is formed, or 



