7 04 OLFACTORY AND TACTILE CENTRES. 



bchafer denies absolutely the conclusions of the above-named experiments. Schafer 

 points out that it is not difficult to substantiate hearing in monkeys ; it is difficult 

 to substantiate deafness, for quite normal monkeys will often fail to pay the least 

 attention to loud sounds. In six monkeys, Schafer asserts that after more or less 

 complete destruction of the superior temporal gyrus on both sides, hearing was not 

 perceptibly affected. In one case, both temporal lobes were completely removed 

 without any permanent diminution in the acuteness of hearing. These results are 

 opposed to the ordinary clinical teaching on this subject.] In man, injuries to the 

 first and second temporo-sphenoidal convolutions on one side do not appear to 

 cause complete deafness of one ear, as it seems that the sense of hearing for each 

 ear is perhaps represented ou both sides. Bilateral lesions of these convolutions 

 in man cause complete deafness. Disease of these two convolutions is associated 

 with word-deafness (p. 713). Wernicke cites the case of a person first affected 

 with word-deafness, who afterwards became completely deaf; and after death, a 

 bilateral lesion was found in the first temporo-sphenoidal convolution. These con- 

 volutions are supplied with blood by the middle cerebral or Sylvian artery. 



[The auditory paths are from the auditory nuclei in the medulla oblongata 

 through the pons, where they perhaps cross into the tegmentum, thence into the 

 " sensory crossway," and onwards to the auditory centre.] 



[Auditory Autsb. Equally important with these effects of disease are the sensory impressions, 

 or "aurte," which sometimes usher in an attack of epilepsy ; sometimes these aurae consist of 

 sounds or noises, and in these cases the seat of the disease is;often in the first temporo-sphenoidal 

 convolution.] 



[3. The olfactory centre has not been so definitely located as some of the 

 others. There is strong presumptive evidence that it is situated in the hippo- 

 campal region of the temporal lobe, at its lower extremity. This view is strength- 

 ened by the anatomical relations of this region to the olfactory tract and anterior 

 commissure (Ferrier). M'Lane Hamilton has recorded a case of epilepsy ushered 

 in by an aura of a disagreeable odour, in which there was atrophy of the grey 

 matter of the right uncinate gyrus.] 



[Olfactory Path. Although the outer root of the olfactory tract runs direct to the uncinate 

 gyrus, in Iwmuuuvsthesia resulting from injury to the "sensory crossway," smell is lost on the 

 opposite side, while it is lost on the same side when the uncinate gyrus is involved. It may be 

 that the impulses go. first to their own side, and cross afterwards.] 



[4. We do not know the centre for taste, and even the course of the nerve of 

 taste is disputed. Ferrier places it close to that of smell.] 



On stimulating the subiculum in monkeys, dogs, cats, and rabbits, he observed peculiar 

 movements of the lips and partial closure of the nostrils on the same side ( 365). In man, 

 subjective olfactory and gustatory perceptions are regarded as irritative phenomena, while loss 

 of these sensory activities, often complicated with other cerebral phenomena, is regarded as a 

 symptom of their paralysis. 



[The gustatory path crosses in the posterior part of the posterior segment of the internal cap- 

 sule. While Cowers admits that the chorda tympani is the nerve of taste for the anterior two- 

 thirds of the tongue, he thinks that it reaches the facial nerve from the spheno-palatine ganglion 

 throngh the Vidian nerve. He denies that the glosso-pharyngeal is concerned in taste, and 

 " he believes that taste impressions reach the brain solely by the roots of the 5th nerve." He 

 admits that the nerves of taste to the back part of the tongue may be distributed with the 

 glosso-pharyngeal, reaching them through the otic ganglion by the small superficial petrosal and 

 tympanic plexus.] 



[5. Ferrier places the centre for tactile sensation in the hippocampal region, close 

 to the distribution of part of the posterior cerebral artery ; so far this has not been 

 confirmed. The centre for the sensation of pain has not been defined ; probably it 

 is very diffuse. The limbic lobe, according to Broca, includes the hippocampal 

 convolution and the gyrus fornicatus. Ferrier found that removal of the hippo- 

 campal region resulted in a diminution of the sensibility of the opposite side of the 



