PHILOSOPHICAL 
TRANSACTIONS. 
I. The Croonian Lecture. On the internal structure of the Human 
Brain , when examined in the microscope , as compared with that 
of Fishes , Insects and Worms. By Sir Everard Home, Bart. 
V.P.R.S. 
Read November 20, 1823. 
A t the time this Lecture was instituted for the discovery of 
the principle on which muscular motion depends, the principle 
was supposed to be inherent in the muscular fibre itself : the 
numerous dissertations, therefore, which are registered in the 
Philosophical Transactions, are in general so many investi- 
gations into the properties of muscular fibres. 
This part of the subject may be considered as completely 
exhausted, although the principle on which the motion de- 
pends is not yet made out. This leads me to believe that we 
must extend our enquiries to the structure of the brain and 
nerves before we can arrive at it. 
It is now, I trust, universally allowed by physiologists, 
that muscular motion cannot take place in living animals 
without the aid of the medullary structure of which the brain 
and nerves are composed. 
MDCCCXXIV. 
B 
