228 
Proceedings of the Royal Society 
which are appended to the second volume of his ‘ Life and Work 
at the Great Pyramid,’ fully entitle him to the highest testimony 
which the Council has in its power to confer.” The Chairman then 
handed the Keith Medal to Professor Smyth, remarking that the 
Council offered no opinion on the important theories he had enun- 
ciated, but recognised the valuable character of the measurements 
he had made. 
The following Communications were read : — 
1. On the Changes produced by direct Chemical Addition 
on the Physiological Action of certain Poisons. By Drs 
A. Crum Brown and Thomas R. Fraser. 
In this paper the authors communicate the iirst results of an 
attempt to discover the relation which must exist between the 
chemical constitution and the physiological action of a substance. 
As the chemical constitution of the majority of physiologically active 
substances is unknown, they investigate the subject by examining 
the physiological action of a substance before and after the per- 
formance upon it of a definite chemical operation, introducing a 
known change into its constitution. The question is thus reduced to 
a problem in what may be called a chemico-physical calculus of 
finite variations. Thus, if the chemical constitution be represented 
by C, the physiological action, P, is some unknown function of C, 
say / C. In order to find f a change is produced on C, by which it 
becomes C + A 0, and the corresponding change of physiological 
action from / C to /C + A/*C is investigated. We here know 
A 0,/C, and A/* C ; and by finding their relations for a sufficiently 
large number of values of C (even where these are unknown), and, 
by varying A C, the function / may be determinded. The change 
of constitution represented by A 0 must be a simple and unam- 
biguous one. There are two kinds of operation to choose between 
— replacement and addition ; and the authors select as the first 
subject of inquiry the effect of addition — that is, such chemical 
change as increases the active atomicity of atoms or radicals. The 
following may be given as simple examples of such operations : — 
