104 CONSCIOUSNESS AND SENSATION. 
of matter properties incomprehensible and of which 
there is no evidence. But it is remarkable that 
neither medicine nor surgery, nor experiments on 
animals, have shown any difference of function 
in the different parts of the hemispheres. Wounds 
of the brain and limited spots of disease do not 
vary in their symptoms according to the part of 
the roof of the hemisphere attacked. I am not 
forgetful of the remarkable phenomena of aphasia 
nor the discoveries of Broca, but I have pointed 
out elsewhere’ that the connection between aphasia 
and lesion of the brain external to the island of 
Reil is, best explained, not by reversion to the 
doctrine of the divisibility of the hemispheres into 
different organs, but by taking into account the 
variety of processes required to go on consentane- 
ously to produce speech, and considering the 
interruption to the consentaneous action of the 
hemispheres by interference with the fibres of 
‘communication at the most central part of the 
organ. 
It is not only in the case of speech but in all 
the more complicated operations of thought that 
the mind has to attend to different matters at 
the same time, and it can well be imagined that 
simultaneous and harmonious action of the brain- 
1 Medical Press and Circular, 11th March, 1870. 
