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XVI. The Croonian Lecture. — Experiments on the Brain of Monkeys (Second Series) . 
By David Ferrier, M.A., M.B . , Professor of Forensic Medicine , King's College. 
Communicated by Dr. Sanderson, V.P.B.S. 
Received April 27, — Read May 13, 1875. 
In a former memoir presented to the Royal Society the author described the results of 
electrical irritation of localized regions of the brain of monkeys. This memoir contains 
the details of experiments relating chiefly to the ablation or destruction of these localized 
centres, with the view of determining the significance, as regards motion and sensation, 
of the phenomena resulting from electrical stimulation, and for the purpose of ascer- 
taining the function of those parts which give no external response to irritation. No 
originality is claimed either for the idea or method of carrying out these experiments. 
The plan chiefly followed in the destruction of localized regions in the hemispheres 
was the application of the cautery, either in the form of a red-hot iron, or of the gal- 
vanic cautery, or of Bruce’s blowpipe cautery, according to special necessities or con- 
ditions. The advantage of this method is that destruction of the grey matter can be 
caused rapidly and effectually, without risk of haemorrhage or interference with the 
integrity of surrounding parts. By the same method a part can be severed from the 
hemispheres without risk of haemorrhage. 
The details of observation are given in full as the best method of indicating the course 
of events following each operation and the data on which the conclusions are based. 
Extirpation of the Frontal Lobes. 
It has already been stated that the antero-frontal regions of the hemispheres give no 
response to electrical stimulation. Only one exception to this statement is to be made 
(see Exp. I.), viz. that in one case irritation of these regions caused the eyes to be turned 
to one or other side, according as the electrodes were placed on the opposite hemisphere. 
Experiment I. 
December 2nd, 1873. — Avery lively, active, and intelligent monkey was placed under 
the influence of chloroform, and the frontal extremities of both hemispheres exposed as 
far back as the anterior extremity of the supero-frontal sulcus (fig. 1), the infero-frontal 
regions being exposed to a corresponding extent. On electrical irritation of the upper 
surface of these regions the eyes were occasionally turned to the opposite side. No results 
could be observed to follow application of the electrodes to the orbital region. 
The exposed portions of the hemispheres were in this instance divided rapidly by 
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