208 ANIMAL PHYSIOLOGY. 



comparative anatomy show them to be properly considered 

 as part and parcel of the cerebral hemispheres. 



It has already been pointed out that in early development 

 the corpora striata make their appearance in the floor of the 

 hemisphere-vesicles ; they are covered with grey matter on 

 the surface, continuous with that which lines the whole 

 cylinder of the cerebro-spinal axis; and they have other 

 patches of grey matter within them, which, when cut across, 

 present the striated appearance from which the bodies are 

 named; and the lowest of these is in communication with the 

 island of Reil, so that a communication is here established 

 between the grey matter lining the cerebro-spinal canal, and 

 that of the cerebral convolutions. We have seen also that 

 in different animals, while the corpora striata and cerebral 

 hemispheres are intimately connected, they are very variously 

 proportioned one to the other; for, in fishes, one pair of 

 structures represents both; in the turtle a small corpus 

 striatum lies at the bottom of each hemisphere, looking into 

 the interior of its vesicle; and in birds, the islands of Keil 

 and corpora striata form the greater part of the hemispheres: 

 indeed, in the common fow], the hemispheres consist of 

 scarcely anything else; and when a physiologist, in vivi- 

 section, slices what he terms the hemispheres from a fowl, he 

 in reality, removes in the upper slices the corpora striata 

 covered with a thin membrane representing the roof of the 

 hemispheres. 



153. The cerebral hemispheres are the parts of the brain 

 connected with the higher operations of intelligence. The 

 experiment just alluded to, as performed on fowls, can be 

 performed less easily on mammals; but the result in both 

 cases is the same, namely, that the larger the part of the 

 hemispheres taken away, the less intelligence remains. The 

 effect of removal of the hemispheres from a pigeon is gra- 

 phically described by Dalton, the American physiologist. 

 " The bird remains sitting motionless on his perch, or stand- 

 ing upon the ground, with the eyes closed, and the head 

 sunk between the shoulders. Occasionally, the bird opens his 

 eyes with a vacant stare, stretches his neck, perhaps shakes 

 his bill once or twice, or smooths down the feathers upon his 

 shoulders, and then relapses into his former apathetic con- 



