io8 ^Journal of Coniparafivc Neurology and Psychology. 



In a similar manner, division of the nlnar nerve produces complete 

 insensibility of the little finger, and of a variable part of the palm 

 and the ulnar half of the ring finger. Such is the usual statement of 

 surgeons and anatomists. . . . The most careful examination of 

 the hand fails to show the slightest diminntion in s(,']isation over the 

 median half of the palm in consequence of division of the nlnar 

 nerve. What has always been called the diminished sensibility 

 produced by the division of a nerve is really a condition in which 

 some kinds of sensibility are lost and others retained." ^ 



The results of careful examinations of about eighty patients, in 

 whom the nei-ves of arm or leg had been divided or injured, led to 

 the following conclusions : "The sensory mechanism in the peripheral 

 nerves is found to consist of three systems : 



''(A) Deep sensibility, capable of answering to pressure and to 

 the movement of parts, and even capable of producing pain under the 

 influence of excessive pressure, or when the joint is injured. The 

 fibers subser\'ing this form of sensation run mainly with the motor 

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

 to the skin. 



"(B) Protopathic sensibility, capable of responding to painful 

 cutaneous stimuli, and to the extremes of heat and cold. This is 

 the great reflex system, producing a rapid widely diffused response, 

 unaccompanied by any definite appreciation of the locality of the 

 spot stimulated. 



"(C) Epicritic scnsihility, by v/hich we gain the power of cutane- 

 ous localization, of the discrimination of two ]wints, and of the finer 

 grades of temperature, called cool and warm." " 



The separate sensation elements in each of the three forms of 

 sensibility may be tabulated as follows : 



"Loss of epicritic sensibility abolishes: recognition of light touch 

 over hairless parts or parts that have been shaved ; cutaneous localiza- 

 tion ; discrimination of compass points ; appreciation of difference 

 in size, including the accurate discrimination of the head from the 



*Heacl, Rivers and Sberren : The Afferent Nervous System from a New 

 Aspect. Brain, 1905, Vol. 28, p. 100. 

 'IMd., p. 111. 



