4 Dr. Philip’s additional experiments on the 
ciples different from those hitherto assumed by physiologist.,. 
What these principles are, I have endeavoured to ascertain in 
the paper just mentioned. One part of the subject I left 
untouched, as it seemed at first sight to open too extensive a 
field of enquiry. It was evident in making the experiments 
related in that paper, that the laws which regulate the effects 
of stimuli applied to the brain and spinal marrow on the 
muscles of voluntary, and on those of involuntary motion, are 
very different. The following experiments point out more 
precisely in what this difference consists. 
Exp. 2. Part of the cranium of a rabbit was removed, and a 
wire passed in various directions through the brain. I could not 
in this way in the least affect the muscles of voluntary motion, 
except when I made the wire approach those parts of the 
brain from which the spinal marrow and nerves originate. 
The muscles of voluntary motion were then thrown into vio- 
lent spasms. I sliced off the whole of the upper and anterior 
part of the brain without affecting the muscles of voluntary 
motion. The knife only excited their action when it ap- 
proached the source of the nerves. 
Having deprived another rabbit of sensibility and voluntary 
motion by a blow on the occiput, that I might be enabled to 
judge of the effects which a stimulus applied to the brain would 
produce on the heart, I removed part of the cranium and laid 
open the thorax. The heart was found beating regularly. By 
passing a wire through the brain in any direction, the beats of 
the heart were accelerated and rendered stronger. I could not 
perceive that this effect was produced more powerfully when 
the wire was directed towards the source of the nerves, than 
when any other direction was given to it, provided it passed 
