BIOLOGY IN RELATION TO OTHER NATURAL SCIENCES. 459 



shown tliat the process of destruction is a chemical one, that the 

 (lestractivc aj^cnt has its source in the cheniiotactic cells — that is, cells 

 which act under the orders of chemical stimuli. Two Cambridge 

 observers, Messrs. Kanthack and Hardy,* have lately shown that, in 

 the particular instance which they have investigated, the cells which 

 are most directly concerned in the destruction of morbific bacilli, 

 although chemiotactic, do not possess the power of incorporating bacilli 

 or particles of any other kind. While therefore we must regard the 

 relatiim between the process of devitalizing and that of incorporating 

 as not yet sufficiently determined, it is now no longer i^ossible to regard 

 the latter as essential to the former. 



There seems therefore to be very little doubt that chemiotactic cells 

 are among the agents by which the human or animal organism protects 

 itself against infection. There are however many questions connected 

 with this action which have not yet been answered. The lirst of these 

 are chemical ones — that of the nature of the attractive substance and 

 that of the process by which the living carriers of infection are 

 destroyed. Another point to be determined is how far the process 

 admits of adaptation to the particular infection which is i)resent in 

 each case, and to the state of liability or imnumity of the infected indi- 

 vidual. The subject is therefore of great comi)]ication. None of the 

 l^oints I have snggested can be settled by experiments in glass tubes 

 such as I have described to you. These serve only as indications of the 

 course to be followed in much more complicated and difficult investiga- 

 tions, when we have to do with acute diseases as they actually affect 

 ourselves or animals of similar liability to ourselves, and find ourselves 

 face to face with the question of their causes. 



It is possible that many members of the association are not aware of 

 the unfavorable — I will not say discreditable — position that this coun- 

 try at present occupies in relation to the scientific study of thfe great 

 subject — the causes and mode of prevention of infectious diseases. As 

 regards administrative efficiency in matters relating to public health, 

 England was at one time far ahead of all other countries, and still 

 retains its superiority; but as regards scientific knowledge we are, in this 

 subject as in others, content to borrow from our neighbors. Those who 

 desire either to learn the methods of research or to carry out scientific 

 inquiries, have to go to Berlin, to Munich, to Breslau, or to the Pasteur 

 Institute in Paris, to obtain what England ought long ago to have pro- 

 vided. For to us, from the spread of our race all over the world, 

 the ])revention of acute infectious diseases is more important than to 

 any other nation. At the beginning of this address I urged the claims 

 of pure science. If I could, I should feel inclined to speak even more 

 strongly of the application of science to the discovery of the causes of 

 acute diseases. May 1 express the hope that the effort which is now 



* Kanthack and Ilartly, "On the Characters and Beliavior of the Wan(hriiig Cells 

 of the Frog, Proceedlngfi of the Koyal SocUty, vol. Lii, p. 267. 



