438 



I have generally made use of refrigerating agents, such as ice and 

 water at O a Cent. The symptoms produced by either of these 

 applications relate to 1st, the sensibility; 2nd, the excitability; 

 3rd, the temperature of the nerve under examination, or of the parts 

 which it supplies. 



Sensory symptoms. The first effect of the application of ice to 

 the ulnar nerve, as is well known, is a state of hypersesthesia de- 

 scending apparently to the inner fingers, which gradually increases 

 until it becomes very painful. After a minute or two the hyper- 

 sesthesia diminishes, and the pain suddenly disappears. 



Sometimes the nerve passes from this condition into a state of 

 complete anaesthesia, when both the nerve and the integuments below 

 are insensible. 



In other cases, before these parts are rendered insensible, we have 

 hypersesthesia and analgesia of the nerve recurring several times 

 before the supervention of the stage of anaesthesia. 



Symptoms of motricity. The first change in the excitability of 

 the nerve, or its power of inducing muscular contractions, is that of 

 increased action on either mechanical or electrical irritation, and is so 

 manifest, that an ordinary degree of irritation, which in the normal 

 state will scarcely produce any muscular contraction, will cause 

 strong movements of the wrist and fore-arm. 



The second stage of nerve -excitability is that in which there is 

 decreased muscular action terminating in its complete loss. 



The passage from the first to the second stage is marked by no 

 distinct symptom, as the one gradually blends into the other. While 

 the nerve is passing through these stages, the muscles subject to the 

 nerve likewise present changes. At the inner part of the fore-arm 

 they slightly contract, and the little and ring-fingers particularly 

 become somewhat flexed and stiff, and their movements imperfect. 

 Finally, these muscular parts become quite paralysed, and the little 

 finger remains permanently flexed. 



Temperature. For the purpose of measuring accurately the tem- 

 perature of the parts supplied by the nerve during the various changes 

 in its condition, very delicate instruments are indispensable. I have 

 used for the present experiments two standard thermometers of M. 

 Geissler of Bonn, in which, although the reservoir is very small, the 

 tenth part of a degree Centigrade is easily read off by the naked eye. 



