102 CONSCIOUSNESS AND SENSATION. 
each in the turtle, and in the bird the whole 
hemisphere-vesicle converted into corpus striatum 
(or, more correctly, corpus striatum and _ island 
of Reil), with the exception of little more than a 
membrane at the upper part. The hemisphere- 
vesicle, therefore, appears to be a single organ 
primarily divisible, as Reichert has beautifully 
shown, into a root-part which includes corpus 
striatum and island of Reil, and the “mantle” 
which includes the remainder; and I apprehend 
that the mantle is only a multiplier of the function 
of the root-part. 
If we now revert to one of the propositions 
made at starting, and bear in recollection that 
while there is every reason to believe that the 
corpuscles of the hemispheres pass into the im- 
pressed condition studied in nerves, there is no 
vestige of evidence that they have any additional 
active condition, it will become apparent that the 
law of operation of the functions of the hemi- 
spheres is that they are so connected with the 
mind that the total amount of mental action at 
one time its dependent on the total amount in the 
hemispheres of that physical state which we call 
the impressed condition. 
Consciousness and the impressed condition 
of brain-substance go always together, but that 
