423 
ACKNOWLEDGEMENTS 
many unexpected quests, and has brought me into 
contact with so many problems and such divers people 
(both living and dead), that I now find it difficult to record— 
or even, I fear, to remember—all the help which I have 
received from others in the course of its compilation. Almost 
everybody I know has contributed—wittingly or unwittingly, 
directly or indirectly—something towards its fulfilment: and 
with negligible exceptions every person whose aid I have sought 
has willingly furnished me with information or material. It 
is impossible, therefore, to mention here by name all the 
friends and colleagues, all the fellow-students and distant co- 
workers whom I have never met in the flesh, all the librarians 
and antiquarian booksellers and editors and publishers, who 
have given me their unstinted assistance at all times. Con- 
sequently, I can only beg them, one and all, to accept now 
this general acknowledgement of my indebtedness. 
But there are some special helpers whose names I cannot 
omit to mention specifically. My debt to my two “ Brothers” 
I have attempted to repay by dedicating this volume to them. 
Without their fraternal encouragement it would never have 
been written, and I therefore owe them both more than I can 
express—big brother D’Arcy for his unattainable example 
and incomparable scholarship in wider fields, little brother 
Paul for his equal enthusiasm on common ground. Next 
after these I would mention my old friend Mr A. Hastings 
White, Librarian (now, alas! in only a consultant capacity) to 
the Royal Society, whose knowledge of everything connected 
with the Society has been of incalculable assistance. I have 
never sought his aid in vain, and he has always placed his 
own vast learning at my disposal most liberally. 
I am further indebted, in no small degree, to several 
good friends in Holland. That great bacteriologist, the late 
i ae book has been so long a-writing, has taken me on so 
