100 The Muscle Sense [CHAP. 



The evidence brought forward in support of the localisation of the muscle sense in 

 parts adjoining the postcentral gyms has a most important and direct bearing on the thesis 

 I have submitted that the latter gyms is a centre for " common sensation," and to my mind 

 strengthens that thesis ; for I can only think that the incongruity concerning the loss of 

 muscle sense, both after a lesion in the Rolandic area and after one in the parietal region, 

 is to be explained by an involvement of my postcentral area, an area which has been neglected 

 previously on account of its supposed motor function, an area, the curious cortical structure 

 of which has not received due notice, and an area which, in spite of what von Monakow says 

 to the contrary, has the closest connections with the " cortical lemniscus." Moreover, the general 

 agreement that a lesion situated primarily in the central gyri, but extending backwards into 

 the parietal lobe, is most favourable for the production of this disability seems very suggestive. 

 As to those cases of pure loss of the muscle sense in consequence of lesions confined to parts 

 of the parietal lobe (superior parietal and supramarginal gyri), after considering them very 

 carefully, I have come to the conclusion that they do not invalidate my thesis, and for the 

 following reasons; first, it is difficult to conceive how a deep-seated lesion in the superior 

 parietal or supramarginal gyms can avoid implicating the tracts of fibres making for the post- 

 central gyrus, and especially those which are destined for the posterior side of that gyms ; 

 secondly, the area, which I have defined as having histological characters intermediate 

 between those of the postcentral area proper and the parietal area, extends in some cases 

 for an appreciable distance on to the gyri in question, and probably to its obliteration the 

 impairment of the muscle sense in these cases is to be attributed. 



Of those who oppose the localisation of the muscle sense, either in the Rolandic zone 

 or in the parietal region, Ferrier may be taken as the leader, and he maintains that the 

 affection of that sense in cases of lesion in these situations is the outcome of coincident 

 disturbance of the functions of sensory tracts and centres situated elsewhere than in the parts 

 actually diseased. But his doctrine of sensory localisation has been already discussed and the 

 criticism need not be repeated. 



Stereognostic Sense. 



The loss of the faculty of distinguishing the form, consistence, etc., of objects is one 

 of those phenomena which certain observers formerly regarded in the light of an accidental 

 accompaniment of a lesion in the Rolandic zone, but as our knowledge of sensation in general 

 and of this sense in particular has advanced, the disability has been placed on a firmer 

 footing and is now recognised as one of common occurrence. As Walton and Paul affirm, 

 the stereognostic faculty must depend upon the integrity of a high combination of senses 

 (the muscle and pressure senses, the power of discriminating points in contact, etc.), and to 

 explain why an individual capable of appreciating the slightest touch may at the same time 

 be unable to distinguish the form and consistence of an article (for instance, a coin, which 

 is the commonest test object) placed in his hand, we can only suppose that an interruption 

 of psychic and associative processes is an essential superadded condition. Being such a complex 

 sense it is readily understood that its localisation is hard to determine ; it has of course 

 only been studied in the human subject, and has been placed by most writers in the Rolandic 

 zone, by others in the parietal lobe, while, in accordance with my view, a destructive lesion 

 in either of these situations would be adequate to its production. 



