CONSCIOUSNESS AND SENSATION. {01 
structure may reasonably be supposed to arise 
from the different relations in which the different 
parts of the hemisphere lie to the corpora striata 
and from unequal development of the nerve-cor- 
puscles ; a supposition in favour of which is the 
circumstance that in the posterior lobes, the parts 
furthest from the corpora striata, the nerve-cor- 
puscles are least developed, and the horizontal 
fibres are most abundant. 
But not only does the study of structure thus 
point to the probability of the whole hemispheres 
having one combined function, but development, 
comparative anatomy, and experiment point to the 
propriety of considering the corpora striata as 
forming with the hemispheres one organ. The 
corpora striata are enlargements of the basal por- 
tions of the hemisphere-vesicles ; so says develop- 
ment: they are inseparable from the islands of 
Reil; so says adult structure. They may be 
irritated or damaged by vivisection in mammals, 
without damage to sensation or motion, and slic- 
ing them away in birds produces effects corres- 
ponding with those produced by slicing away the 
hemispheres in mammals; that is the evidence 
of experiment : while comparative anatomy shows 
the hemisphere-vesicles forming each a unity in 
fishes, a small distinct corpus striatum within 
