474 
DR. D. FEEEIEE ON THE BRAIN OF MONKEYS. 
On opening the ventricles they were found free from effusion. The left optic 
thalamus was disorganized. 
The track of the hot iron was easily traced by its blackened appearance. It had 
passed horizontally almost in the centre of the ventricular aspect of the ganglion, a line 
or so beneath the surface, and completely traversing the left thalamus, had just 
crossed the third ventricle and made a slight indentation on the opposite right 
thalamus. 
Besides this wound there was another lacerated surface situated more towards the 
extraventricular aspect of the thalamus. This had been caused by the spring stilette, 
which, as it had been conjectured, had not penetrated the body of the ganglion. Bound 
this discoloured laceration softening had extended somewhat, but had not quite invaded 
the body of the thalamus. The anterior and posterior extremities of the thalamus were 
almost of normal appearance. The intervening portion was quite broken up. 
The corpora ' striata and corpora quadrigemina were uninjured. The crura cerebri 
were intact. 
In this experiment the lesion was confined to the optic thalamus, or as far as can be 
effected by such a method of experimentation. 
This result, and the result of Experiment XVI., show that complete disorganization 
of the optic thalamus in monkeys abolishes cutaneous sensation on the opposite side. 
(As I am restricting my conclusions to monkeys, I do not here stay to discuss in detail 
the results of Nothnagel’s experiments on rabbits (Virchow’s Archiv, 1874, p. 201), 
which lead him to apparently contradictory conclusions. I will merely remark, on the 
ground of experiment, that Nothnagel, in my opinion, is not warranted in asserting 
that true sensation continues in rabbits after total destruction of the optic thalami. 
Beaction to tactile stimuli, in all respects resembling sensory, such as springing forward 
when the tail is pinched, or uttering screams, still continues to be manifested by these 
animals after complete removal of the hemispheres.) 
The retention of reaction to stimulation in the first instance in this experiment may 
have been due partly to reflex action, partly to the retention of sensation ; but that 
sensation was impaired was evidenced by the fact that the animal ceased to use its right 
limbs as before for the purposes of prehension and touch. Here also, as in destruction 
of the hippocampal fold, there was apparent muscular paralysis — but not so in reality, 
as the animal could still move the limbs in some degree, and the muscles retained 
their tonicity and resistance. 
The interference with vision may have been due to the proximity of the lesion to the 
angular gyrus and its medullary connexions, as much as to the lesion of the optic tha- 
lamus, and therefore no definite conclusion is built on this fact. With regard to the 
circular movements of the animal which were occasionally made, the body seemed to go 
to the right or left according as the left arm was adducted or abducted. 
The next experiments relate to the effects resulting from destruction or complete 
removal of the occipital lobes. 
