of Edinburgh, Session 1869 -70. 
145 
Monday , 1 8th April 1870. 
Professor KELLAND, Vice-President, in the Chair. 
The following Communications were read : — 
1. Facts as to Brain- Work ; in Illustration of the New and 
Old Methods of Philosophical Inquiry in Scotland. By 
Thomas Laycock, M.D. 
A few words in explanation are needed. In my summer course 
of lectures on Medical Psychology and Mental Diseases delivered 
in the University, I have to investigate the human mind in its 
practical relations to the body, and especially I have to teach how 
each influences the other, so that the physician, or any intelligent 
person, may be able to modify these relations beneficially. The 
starting-point in these inquiries is the fundamental fact of ex- 
perience, that no changes in the mind or the consciousness of what- 
ever kind can or do arise, or continue, without a corresponding series 
of changes somewhere in the brain-tissue. This fact being held as 
certain as the fact of gravitation, the solutions of the problems to 
be solved depend upon a knowledge of the relations which the 
two series of phenomena bear to each other ; for which knowledge 
it is necessary to analyse and classify the varying states of con- 
sciousness on the one hand, and the changes in the brain-tissue 
which correlate them on the other. As to the last mentioned, it 
is certain that they are vital; they come, therefore, under the 
sciences of Life collectively termed biology. 
But all molecular changes in living tissues, of whatever kind 
they may be, and consequently those of the brain, can be brought 
also within the circle of molecular physics, for they can all be 
resolved into motion of something, whether we designate that 
something an atom, a molecule, a vortex, a ring, or a centre of 
force. They are due, therefore, to energy; or, as distinct from 
mind, to motor energy. The Bev. Professor Haughton, M.D., of 
Dublin University, was led by experimental research to the con- 
clusion, that as much motor energy is expended in brain-work in 
