4 
PROFESSORS V. HORSLEY AND E. A. SCHAFER 
observation for nearly four months without showing any abnormal symptoms 
whatever. The extent of the lesion in these two cases is shown in figs. 1 and 2 ; 
and the extent in a third experiment upon this region in fig. 3 (Plate 1). As was 
d fortiori to have been expected, unilateral ablation, which we performed in one case, 
proved equally devoid of positive results. 
Conclusions and I'emarhs. — The results of our experiments upon the anterior part 
of the frontal lobes have been completely negative so far as electrical excitation or 
the permanent result of ablation are concerned. In this we are in agreement with 
Ferkier and Yeo/"' but in contradiction of the results obtained by H. MuNK.t 
Fereier and Yeo, it is true, describe certain transient symptoms as having been 
observed by them, but we have already given our reasons for regarding such 
immediate and only transitory effects as not to be laid too much stress upon in the 
determination of the function of a part. And they expressly state that in the 
Monkeys which they were successful in keeping alive for any considerable time no 
physiological defect of any kind could be substantiated.! Munk, on the other hand, 
has described positive symptoms as resulting from extirpation of this part of the 
cerebrum both in Dogs and Monkeys, viz., a paresis of the trunk muscles, cavising 
loss of rotating power if the extirpation be unilateral ; and with bilateral removal in 
Monkeys a peculiar cat-hke bending of the trunk. § Munk also found that electrical 
excitation caused contraction of the muscles of the back and abdomen, and even the 
diaphragm, but admits that very strong excitations are necessary to produce any effect. 
He attempts to explain the necessity for such strong excitation by the gi'eater weight 
which the trunk muscles have to move (in proportion to their number and size ?), 
but it seems to us that a much simpler explanation may be given, and that the 
results which he describes are due to the spreading to other regions of the brain of the 
strong currents which he confesses to have been obliged to employ. The governance 
of the trunk muscles, which Munk has ascribed to the prefrontal region, belongs rather, 
as we shall immediately show, to the middle of the marginal convolution and the 
adjoining part of the external surface of the hemisphere. The discrepancy between the 
* Fereier and Yeo, " A Record of Experiments on the Effects of Lesion of different Regions of the 
Cerebral Hemispheres," ' Philosophical Transactions,' 1884. See also Fereier, ' Functions of the Brain,' 
p. 396. It would seem that the whole of the prefrontal region was not removed in all the cases 
cited by Professors Feeeier and Yeo, for in many the orbital surface is left intact. On the other hand, 
in some the lesion encroaches above and posteriorly on the centre for movement of the head and eyes. 
t H. Munk, " Ueber die Stirnlappen des Grosshirns," ' Sitzungsberichte der k. PreussiscLen Akademie,' 
1882. 
X See especially their remarks upon Case No. 22 recorded by them, in which the lesion of the prefrontal 
region was very complete. 
§ Probably the attitude we have described in the note on the previous page. Munk also affinns 
that cutaneous and muscular sensibility is lost in the trunk after this lesion, and indeed in all these cases 
of cortical lesion refers the resulting muscular paralysis to the loss of such sensibility ; this is, however, 
a question which will be discussed later on. 
