NERVE OVERLAP— PAIN SENSE— PERIPHER.\L NERVES 359 



Finally, they state (page 140) that ''Division of the nerve (one 

 of the nerves of the hand) leads at once to the production of an 

 area of absolute cutaneous insensibility, surrounded by an area 

 of loss of sensation to stimuli, such as light touch and the minor 

 degrees of temperature. The relative extent of these two areas 

 differs greatly in each individual case, and the first definite sign 

 of reco\^ery is shown by an increase in size of the intermediate 

 zone between them." 



It can be seen that, although it is admitted that some return of 

 sensibility to pin prick may be the result of nerve overlap, the 

 extent of this return and the limit of time wherein this return 

 may take place is not defined. If any overlapping of peripheral 

 nerves is possible it becomes necessary to define the fullest 

 possible extent of this overlap and the limit of time for its 

 occurrence. 



It must be emphasized that this problem is not concerned 

 with the question of whether any degree of pain sense is lost 

 throughout the whole area of the accepted sensory distribution 

 of a nerve wherein tactile sense is always lost. Cobb (3) has 

 pointed out again that "by ^'arying the quantitative value for 

 the stimuli, dissociation of sensations can be predicted and pro- 

 duced almost at will;" that by using low degrees of pressure they 

 can obtain charts whereby painful stimuli and tactile stimuli 

 produce co-extensive areas of anesthesia. This would tend to 

 show that pain sense as well as tactile sense is lost in a co-exten- 

 sive area following di\'ision of a mixed nerve. But it must be 

 admitted that even if this is the case, pain sense cannot be 

 entirely lost in the intermediate zone, else painful stimuli with 

 higher degrees of pressure, insufficient to produce pressme pain, 

 would not be perceived. However closely may the analgesia to 

 stimuli to low degrees of pressure correspond to the anatomical 

 distribution of a ner\'e, the presence of any sensitiveness to pin 

 prick, which is not due to pressure pain, requires explanation. 



I maintain that not only the immediate presence, but the 

 return of sensibility to prick pain alike, which occurs before the 

 return of tactile sensibility, occurs in regions which occupy the 



