516 Origin and Descent of the Human Brain. [July, 
bral bodies it necessarily follows that sensations passing in from a 
variety of points must be distributed to a wider area of central 
points in the medulla and spinal cord. This explains why 
injury to the lateral lobes may occur without manifestation of the 
lesion and why a disorder of the central lobe or vermis produces 
a staggering gait. The main bundles of ingoing nerves are 
gathered in the latter region, while the plexus of fibers in the 
lateral lobes afford many avenues for impulse passage, other than 
those injured or destroyed. The original globular appearance of 
the lobes composing the cerebellum may be well made out in 
most quadrupedal forms, but as we pass to man we see that these 
lobes have become compressed into laminz. 
In a previous paper (presented to the American Association for 
the Advancement of Science, Boston, August 28, 1880, published 
in the Yournal of Nervous and Mental Disease, October, 1880, 
and American Narurauist, January and February, 1881), 1 en- 
deavored to show that all tubercles of the vertebrate brain fall 
within this category of intervertebral, a notable instance being the 
Gasserian ganglion. Mr, A. Milnes Marshall ( Monthly Microscopt- 
cal Yournal, London, October, 1877), in an article “ On the de- 
velopment of the nerves of the chick,” shows plainly that 
the olfactory nerve must be considered homologous with spinal 
nerves, for it is similarly developed and in no way differs from a 
spinal nerve. Nor does the comparison rest here, for the lobe 
(not bulb) of the mammalian olfactory niay be seen to be de 
veloped between the central tubular gray and the periphery jost 
as is an invertebral. As to internal structure, the law of dif 
ferentiation shows that subsequently acquired differences are not 
arguments against original derivation, for what can be more UM 
like than bone and cartilage, skull and vertebra or hand and foot ? 
And yet the one is a developed or differentiated condition of 
the other. 
Thus the mammillary eminences, the epiphysis, the optic and 
post-optic lobes were originally intervertebral, and the olwat 
body embedded in the spinal gray is another related particularly 
to innervation of the tongue. It is very large in the parrot 
has relation to the ability of that bird to articulate. But the mos — 
general interest centers in this large mass of nerve fibers and er 
called the cerebrum. In the Ornithorynchus, it is smooth at 
simple in form, but the beaver also has an unconvoluted bratty 
