690 The Relations of Mind and Matter. [July, 
nected by a thick commissure of nerve fibers. The cerebral cells 
are pyramidal in shape, the summit of the pyramid being directed 
upwards. Each of these cells gives off a delicate fringe of fibrils 
like the fine rootlets of a plant, which spread out in an inter- 
laced network and form a continuous fine plexus. These fibrils 
are believed to be the origin of the sensory nerves, becoming 
aggregated and covered with a medullary sheath. In addition to 
the processes which thus break up into rootlets of protoplasm, 
- there is always one at least which does not thus subdivide but 
continues as.a defined nerve fiber from the cell outward. This is 
believed to be the origin of the motor nerves. The above beliefs, 
however, as yet need substantiation in discovery. 
Midway in the cerebral organ, occupying the center of the 
hemisphere, are two oval-shaped bodies, known respectively as 
the optic thalamus and the corpus striatum. Each is composed 
of several ganglia, the first being connected by nerve fibers with 
the posterior, the second with the anterior portion of the spinal 
chord. These, according to the hypothesis of M. Luys, are in- 
termediate stations for the nerve currents. All the sensory nerves 
of the body are gathered into the ganglia of the optic thalamus, 
from which they are again distributed to the cerebral lobes. The 
return nerves from these lobes are, on the contrary, gathered into 
the corpus striatum, from which they are distributed to the mus- 
cles of the body. It is not necessary to give the somewhat ques- 
tionable conclusions which he draws from this mechanism of the 
cerebral nerve system. 
If now we trace the nervous system downward through the 
different classes of the animal kingdom, its complexity of organi- 
zation is found to gradually decrease. A head ganglion, sending 
off nerves to the organs of special sense, is found to exist in the- 
arthropods and the higher mollusks and annelids, but it has lost 
_ the distinctive features of the vertebrate brain. There is no longer 
a separate cerebral organ above, and only connected by fibers 
with, the ganglia which directly receive sensation and control 
motion. Only the analogue of the basal vertebrate brain seems 
to exist in these lower animals. In the Vertebrata the cerebrum 
= . may be removed without detriment to the functions of animal life, 
and possibly without entire removal of consciousness. In this 
Condition a vertebrate animal may be in nervous analogy with 
= normal condition of the lower animals mentioned, though 
