190 General Consideration of Function [CHAP. 



exactly dominate the sense of smell, and as to the localisation of the gustatory function the 

 knowledge we possess is even less secure. However, now that we have a clearer idea of 

 the structure of the cortex covering these parts, it will be interesting to see whether the 

 truths revealed by the microscope are of any assistance in enabling us to arrive at a closer 

 understanding of their function, and especially whether subdivisions disclosed by histology 

 can be fitted to physiological doctrine. 



Experimental Evidence. 



It might be expected that experiment would not be likely to afford much information 

 concerning the localisation of a sense so obviously difficult to test as the olfactory ; however, 

 attempts have been made to throw light on the subject by this method, and the first we 

 have to refer to are those of Ferrier. Ferrier found that by electrical irritation of the 

 anterior extremity of the hippocampus in the lower ape, it was possible to excite movements 

 of the nostril, particularly on the same side, which suggested subjective olfactory sensation. 

 He also observed that an ablation of this region was followed by loss of the power of 

 perception of odours and of recognition of tastes, and he held, as an outcome of these experi- 

 ments, that the olfactory and gustatory cortical centres were located at the lower extremity 

 of the temporal lobe. 



More recently, Gorschkow, working in Professor Bechterew's laboratory, has published an 

 account of a number of experiments on dogs which in some measure confirm Professor 

 Ferrier's findings. For he arrives at the conclusion that ablation of the lobus pyriformis is 

 attended by loss of the sense of smell on the same side and diminution on the opposite side. 



This, and other experimental work which might be quoted, affords confirmation of the 

 localisation of the olfactory sense somewhere in the hippocampal lobe, but, as I shall point 

 out further on, it is not the best proof that can be produced, and indeed skilled experimenters 

 admit that the method is crude for the purpose and can never lead to the precise localisation 

 of a sense with such complex associations and so difficult to test. 



Mention must here be made of some remarkable results obtained by Professor Ferrier 

 in consequence of destructive lesions of the hippocampus ; these were an impairment or 

 abolition of tactile and general sensibility associated with a condition of the limbs which 

 pointed to loss of the sense of movement without actual motor paralysis. Such results are 

 difficult to explain because they cannot be brought into line with known facts concerning 

 the course and destination of the tracts of fibres which convey impressions of common 

 sensation, and from the anatomical standpoint one might hazard the opinion that the 

 disturbances were attributable to an accidental implication of the tract of sensory fibres 

 running close at hand in the crus. cerebri. Other experiments assigning a sensory function 

 to the gyrns fornicatus are discussed in the chapter on the postcentral area. 



Clinico-Pa thologicu I Data. 



The proof supplied by an examination of patients at the bedside followed by an 

 autopsy is likewise of an unconvincing and unsatisfactory nature, but at the same time cases 

 have been put on record which are, to say the least, suggestive ; of these the following 

 may be mentioned. In a case of tumour of the base of the right temporal lobe destroying 

 the uncus and gyrus hippocampi, recorded by Siebert, substances employed to test the sense 



