84 PERSONAL APPEARANCES IN HEALTH AND DISEASE. 



enlargement of the blood-vessels, i.e., they are dilated. 

 The influence of the sympathetic nerve has been taken 

 off their contracting walls, and just as a limb is para- 

 lysed when its nerves are injured, the coats of the blood- 

 vessels are paralysed. But when the nerve is stimu- 

 lated, the vessels contract, and the previously engorged 

 ear becomes cold, pale, and white, less blood passing 

 through it. And now we come to another fact which 

 must be accepted before we can explain the reason why 

 the hand gets red when it is vigorously rubbed. It is 

 this : although the cerebrospinal nervous system has no 

 direct influence over the involuntary muscles supplied by 

 the sympathetic nerve, it has an indirect influence. It 

 possesses the power of arresting, or diminishing, or, as 

 it is called in scientific phrase, " inhibiting " the action of 

 the sympathetic nerves. Now the act of rubbing the hand 

 stimulates the fine sensory filaments of the sensory nerves 

 in the skin ; their stimulation exciting them to increased 

 function, they inhibit the action of the sympathetic nerves 

 governing the blood-vessels in that part ; and the control 

 of the sympathetic being temporarily suspended, the 

 arteries dilate, and becoming capable of receiving more 

 blood than usual, the part they supply becomes tem- 

 porarily red and hot. The same explanation holds for 

 the effects of other kinds of irritation or stimulation of 

 sensory nerves, e.g., the red blush produced Ity the ap- 



