16 
TUMOUR IN TIIE LATERAL VENTRICLE. 
terior columns of the cord. We continue to trace the fibres 
of these columns upwards to eight particular bodies at the 
head of the cord, close to the arch of the pons varolii, viz., 
four pyramidalia, two olivaria, and two restiformia. The 
pyramidalia are usually described as two only, but these are 
again divided into anterior and posterior pyramids, from the 
course the fibres take proceeding from this part of the 
medulla oblongata. The fibres from the anterior pyramids 
that ascend enter the corpora striata, while those of the pos¬ 
terior proceed upwards into the thalami optici. Those fibres 
that descend from the anterior pyramids form, or are con¬ 
tinued in, the anterior columns of the spinal cord, whilst 
those descending from the posterior pyramids enter the pos¬ 
terior columns. So that the fibres of the anterior pyramids 
are motor, the nerve-force of volition, and those of the 
posterior pyramids are sensory fibres, or the conductors of 
sensation. The corpora olivaria, the lateral eminences of the 
medulla oblongata, send their fibres upwards in the motor 
tract to the cerebellum and to the nates et testes, and down¬ 
wards into the anterior motor columns of the cord. The 
fibres of the restiformia proceed upwards to the cerebellum, 
and downwards to the posterior columns of the cord, and 
there is an important band of fibres that descend to the 
anterior columns of the cord. So far we have made out the 
connexion between the motor ganglia of the cerebrum, 
called corpora striata, and the anterior or motor columns of 
the spinal cord; also between the sensory ganglia, called 
thalami optici, and the sensory or posterior columns of the 
cord. And by observing the communication of the sensory 
and motor columns of the cord, with the other portions of 
the brain, through the corpora olivaria and restiformia, the 
nature of the action, or nerve-force, transmitted by those 
parts of the encephalon, is readily made out. But the great 
sensory and motor ganglia of the cerebrum, the thalami 
optici and corpora striata, besides sending fibres to the 
medulla oblongata, also send fibres upwards into the con¬ 
volutions of the cerebral hemispheres, the seat of intellect ; 
and it remains to be mentioned, that the fibres from the 
hemispheres, the ganglia, and the lobes of the cerebellum, 
decussate each other—those of the right pass to the left side, 
and those of the left pass to the right side; and thus we 
account for lesions of one side of the brain presenting their 
phenomena on the opposite side of that body. 
It is by an intimate knowledge of the functions of the 
several parts of the brain and nervous system, that we are 
enabled to form any correct opinion of the source of those 
