20 
PROFESSORS T. HORSLEY AND E. A. SCHAFER 
more or less complete.* But, as their experiments were performed by a less exact 
method than that of simple excision, and since moreover in none of their experiments 
upon this region did the animals survive more than a few days, it occurred to us to 
approach the same part from the outer side after removal of the lateral portion of the 
temporo-sphenoidal lobe, instead of from behind through the occipital lobe, and we 
accordingly endeavoured in the first instance to determine what effect, if any, is obtained 
by removal of this portion. Oar results have proved uniformly negative so far as the 
larger portion of the lobe is concerned. The animals have exhibited no signs of motor 
paralysis nor any loss of general or tactile sensibility.t We have usually left the 
whole or part of the superior temporo-sphenoidal gyrus and the anterior extremity of 
the lobe, but in one of our cases the superior gyrus was almost completely removed 
upon both sides, only the narrow posterior extremity, for about f -inch in length, being 
left upon the right side. In this case the animal certainly appeared to hear quite 
distinctly, and so far as it goes the experiment is at variance both with the results of 
Ferrier and with those of Munk. But we have not as yet systematically pursued 
the question of the cortical localisation of auditory sensations, although it is right to 
state that such incidental observations as we were able to make upon this function 
have almost uniformly proved negative.^ We have not, as the result of any bilateral 
operation, been able to convince ourselves that deafness has been established in a single 
case.§ This is indeed a very difficult point to determine in many intact Monkeys, 
which, when their attention is attracted by other causes, will often fail to give 
evidence of the hearing even of loud noises, while, on the other hand, other individuals 
readily show that they are conscious of the slightest unusual sound. 
In our earlier experiments upon the hippocampal region we were satisfied, after 
removing the external part of the temporo-sphenoidal lobe, and exposing the hippo- 
campus major by opening up the descending cornu of the lateral ventricle, with 
removing as much of the hippocampus major as could conveniently be got at, usually 
* Feruiki:, ' Phil. Trans.,' 1875, and ' Functions of the Bi-aiii,' pp. 327 et seij. Frrriei: and Yeo, ' Phil. 
Trans.,' 1884. 
t That is, after the shock of the operation was recovered from. 
X Dr. Ferrier is mistaken in the statement (' Functions of the Brain,' 2nd edition, pp. 310, 311) that 
we have been able to corroborate his observations upon the localisation of this function in the supei'ior 
temporo-sphenoidal gyrus in Monkeys. We have so far neither obtained any distinct corroboration nor 
refutation of them, but regard the question as still open ; and, as we have stated in a preceding note, 
one of us is now engaged in a further investigation regarding the localisation of this and other special 
sense functions. The same statement will also hold good with regard to the localisation of olfactory 
and gustatory sensations. Unilateral lesions are probably of but little value in elucidating these 
functions ; at least, we have been unable to obtain any determinate results from them. 
§ It is right to add that we were not specially intending to investigate this point (the localisation of 
auditory perceptions), and that the lesions of this lobe which we record were performed with another 
object, viz., to arrive at the hippocampal region, But, as we have been careful to note all the symptoms 
that we could observe, they are not without their value on this point. 
