426 SCIENCE PROGRESS 



must have been produced in the peripheral segment, which 

 would be ready to exercise their functions directly they are 

 placed in continuity with the fibres of the central end. 



Examination of these cases shows, however, that sometimes 

 the conclusion has been a hasty one, depending largely on the 

 evidence of the patients themselves, in whom the wish is father 

 to the thought. There was a case of this kind recently in 

 King's College Hospital. Very shortly after the operation the 

 patient stated he was able to feel, but these sensations rapidly 

 subsided, and sensation did not really return until months later. 

 The preliminary sensations were doubtless subjective ; the 

 irritation of the nerve in the scar lasted some hours, and the 

 sensations so produced were referred by the patient's mind to 

 the original terminals of the fibres. 



In other cases the genuineness of the early recovery is 

 doubtful, because insufficient care is taken in testing the patient's 

 sensations. In spite of sensitiveness to such tests as needle 

 pricks, there is usually absolute anaesthesia to the far more 

 delicate test of stroking the hairs over the affected region until 

 quite late dates. Head and Sherren have recorded a large 

 number of surgical cases, but evidence of early recovery is 

 usually lacking ; there is some difficulty in localising the stimulus 

 so that it should not affect the hyperaesthetic marginal zone of 

 the anaesthetic region, and if this danger is recognised it can 

 be avoided. Another pitfall is this : the deep sensibility of the 

 subjacent parts, such as would be excited by needle pricks, 

 or by pressure, is entirely independent of cutaneous sensation. 

 The fibres subserving this form of sensation run mainly with the 

 motor nerves, and are not destroyed by division of all the nerves 

 to the skin. Neglect to recognise this fact will explain some of 

 the results of those who have published cases of early recover3^ 

 The difficulty of clinical observation on others induced 

 Dr. Head to combine with his experiments on animals and his 

 observations on patients, an experiment on one of the sensory 

 nerves of his own arm. This gave an opportunity for the study 

 of the phenomena by a trained observer upon himself. He 

 certainly experienced no early return of function, and the date 

 at which sensation did come back coincides closely with the 

 dates obtained in animals by physiologists for the reappearance 

 of new and fully formed nerve fibres. 



In the course of this work he made the interesting dis- 



