180 Transactions of the Society. 



of the whole animal world, with man as the most profoundly 

 concerned. 



Of the septic series as such, I have a long-continued incidental 

 familiarity. It is the monad group that I have of course, so far as 

 I have been able to go, thoroughly studied. Yet it would be 

 difficult for any one not a pathologist, and without the resources 

 of a pathological laboratory, to claim to be in the modern sense a 

 bacteriologist. But it may well be doubted whether that modern 

 sense is a really useful and correct one. The bacteria are without 

 much question a botanical group, and to be thoroughly understood 

 must be studied as such. Whoever has studied the same field of 

 septic bacteria for say a week or a fortnight without change of 

 conditions, will know the strange complexity of relations that are 

 seen to arise. I do not profess to interpret them — I have avoided 

 the immense temptation to try to do so, the better to use such 

 facility as I could command in the more complete working out of 

 the monad group. But I feel assured that until this complexity 

 of relation in common forms is understood, we cannot make really 

 assured advance. How the bacteria are interrelated, how far they 

 are mutable, and under what conditions ; and whether functional 

 changes are as readily, or more readily, induced, than morphological 

 changes, are questions of the largest moment. 



I should wantonly occupy your time if I attempted to call your 

 attention to the fact that all this bears upon that special modifica- 

 tion of the septic group only, known at present as bacteria or 

 bacilli, which are pathogenic in their functions. 



In some instances possessed of a specific functional power, they 

 are the direct excitants, the positive virus, of definite forms of 

 disease. To the study of these and their behaviour and life-histories 

 there is a strong and a natural tendency. But it is to the specific 

 and perhaps biologically highly modified form alone that all the 

 labour is directed. 



What is its relation to the whole group ? Has it become modi- 

 fied from normal septic forms ? if so, by what means ; these are 

 in the broad and deep interests of science even larger questions 

 than the morphology and functions of a definitely discovered and 

 demonstrated bacilh-virus. 



Manifestly the work cannot be done by any one group of 

 observers : the pathologists do wisely and well, to pursue their own 

 department of the research with exemplary zeal : but the micro- 

 scopical botanists have such a rich field of inquiry before them, and 

 one so large in its importance, as has scarcely fallen to them before 

 in the entire histoiy of the Microscope. 



That there is a direct and discoverable relation between the 

 septic and the pathogenic bacteria it would be puerile in these days 

 to doubt. What is that relation ? In some instances, certainly, the 



