7220 
escaped the notice of some of the ablest ana- 
tomists, the corpora striata are of good size 
proportionally to that of the entire brain. 
orpora quadrigemina——The marked con- 
nection of these gangliform bodies with the 
optic nerves plainly indicates that they bear 
some special relation to those nerves, and to 
the sense of vision; and this indication be- 
comes more certain when we learn, from com- 
perative anatomy, that in all vertebrate tribes 
mm which the encephalon is developed, special 
lobes exist, bearing a similar relation to the 
optic nerves. When the optic nerves are large, 
these lobes are large; and in the Pleuronecta, 
in which the eyes are of unequal size, Gottsche 
states that the optic lobes are unequal, and are 
related in size to each other, as the eyeballs are. 
Still,as Serres has remarked, the quadrigeminal 
tubercles probably perform some other office 
besides that which refers to vision; inasmuch 
as the absence, or extremely diminutive size, 
of the optic nerves in some animals (the mole 
for instance) does not materially affect that of 
these bodies.* 
Flourens found that destruction of either of 
these tubercles on one side was followed by 
loss of sight of the opposite side, and con- 
sequently that the removal of both deprived 
the animal altogether of the power of vision, 
but didenot affect its locomotive or intellectual 
powers, nor its sensibility, except to light. In 
these experiments the action of the iris was 
not impaired if the tubercles were only par- 
tially removed; as long as any portion of the 
roots of the optic nerves remained uninjured, 
the iris continued to respond to the stimulus 
of light, but the total removal of the tubercles 
paralysed the irides. If the lobes of the brain 
and cerebellum were removed, leaving the 
tubercles untouched, the irides would continue 
to contract. These experiments leave no room 
to doubt that the optic tubercles are the ence- 
phalic recipients of the impressions necessary 
to vision, which doubtless are simultaneously 
felt by means of the optic thalami; and that 
they are the centres of those movements of the 
iris which contribute largely not only to pro- 
tect the retina, but likewise to increase the 
perfection of vision. The optic nerve is at 
once the nerve of vision, and the excitor of 
motor impulses which are conveyed to the iris 
by the third nerve, which takes its origin very 
near to the optic tubercles. It is interesting 
to add, that irritation of an optic tubercle on 
one side causes contraction of both irides :— 
this is quite in accordance with the well- 
established fact, that, if light be admitted to 
one eye so as to cause contraction of its pupil, 
the other pupil will contract at the same time. 
So simultaneous is the action of the two cen- 
tres; so rapid must be the transmission of the 
stimulus from one side to the other. 
When the injuries inflicted on these tuber- 
cles were deep, more or less general convulsive 
movements were produced; if one tubercle 
were injured, the opposite side only was so 
affected. These convulsions were due to the 
* Vid. Optic NERVEs. 
PHYSIOLOGY OF THE NERVOUS SYSTEM. 
lesion of the central parts of the medulla ob- 
longata, with which the optic tubercles are in- 
timately connected. A remarkable vertiginous 
movement was likewise caused, the animal 
turning to the side from which the tubercle had 
been removed. It does not appear that this 
rotation could be attributed to any special in- 
fluence of the medulla oblongata, but rather to 
a state of vertigo induced by the partial destrue- 
tion of vision; for Flourens found that the 
same effects could be produced in pigeons 
blindfolding one race The movements, rie 
ever, were not so rapid, nor did they continue 
solong. And Longet saw the same movements 
in pigeons in which he had evacuated the hu- 
mours of one eye.* . 
It may be remarked, that deep injuries to 
the quadrigeminal tubercles are very likely to 
ma the only commissural connection between 
e cerebrum and cerebellum (processus cere- 
belli ad testes), the integrity © which must. 
doubtless be essentially necessary to ire 
harmony of action between these two great 
nervous centres, ond 
There are many instances on record in 
blindness was coincident with pathologic: 
alteration of structure in one or both quadrigs 
minal tubercles. In some of the cases w 
the lesion extended to parts seated beneat 
tubercles, disturbed movements were obser 
as in the experiments above related. a 
We are ignorant of the object of the ex 
sive connections of the optic tracts with | 
tuber cinereum, the crura cerebri, and 
wet agarip-ad. but these points are hig 
worthy of future inquiry, especiall th 
ference to the office of these inst all DO 
which is at present involved in much obseuri 
Many of the fibres of the optic tracts an 
doubtedly commissural between the coi 
ponding points of opposite sides, and 
when those which form the optic nervy 
deficient. y 
We see, then, in the quadrigeminal tubere 
centres, which, whatever other functions th 
may perform, have a sufficiently obvic 
tion to the optic nerves, the eye, and the 
of vision. This is clearly indi by 
tomical facts, especially by those of ¢ 
tive anatomy, by the results of experiment 
by the phenomena of disease. b 
may, therefore, be justly reckoned as 5} 
ganglia of vision; and we are led to se 
similar centres in connection with the | 
senses. The olfactory processes : 
probably to perform a similar office in r 
to the sense of smell. Their struct re, 
relation to the olfactory nerves, and thei 
proportion of bulk to that of these nervy 
to the developement of the o apr 
place this question beyond all doubt. It 
so easy to determine the special ganglia 0 
ing; but the olivary bodies, or the sr 
bules connected with the crura cerebelli ¢ 
by Reil the flocks, may be referred to as b 
a sufficient close anatomical relation | 
. 
A 
e, 
col 
~ 
* Flourens’ experiments have been amply 
firmed by those of Hertwig and Longet. 
Ls 
