FUNCTIONS OF THE SYMPATHETIC SYSTEM. 437 



direct action is concerned ; but some important points have 

 been developed by observations on reflex vaso-motor phenom- 

 ena, involving a transmission of impressions to the centres 

 through the nerves of general sensibility. 



Reflex Phenomena operating through the Sympathetic 

 System. We shall not discuss, in this connection, the reflex 

 phenomena of secretion, as these have already been consid- 

 ered with sufficient minuteness in another volume, 1 nor 

 again treat of reflex action, through the sympathetic, upon 

 the general circulatory system, which has been taken up 

 fully under the head of the depressor-nerve of the circu- 

 lation, described by the brothers Cyon, 2 but shall here de- 

 scribe certain reflex acts, involving vaso-motor phenomena, 

 which we thus far haA^e touched upon very briefly. 



In treating of animal heat, the phenomena of which are 

 intimately connected with the supply of blood to the parts, 

 we have mentioned the observations of Brown-Sequard and 

 Lombard, who found that pinching of the skin on one side 

 was attended with a diminution in the temperature in the 

 corresponding member of the opposite side, and that some- 

 times, when the irritation was applied to the upper extremi- 

 ties, changes were produced in the temperature of the lower 

 limbs. Tholozan and Brown-Sequard found, also, that low- 

 ering the temperature of one hand produced a considerable 

 depression in the heat of the other hand, without any nota- 

 ble diminution in the general heat of the body. Brown- 

 Sequard showed that by immersing one foot in water at 41 

 Fahr., the temperature of the other foot was diminished 

 about 7 Fahr. in the course of eight minutes. 3 These facts 

 show that certain impressions made upon the sensory nerves 

 afiect the animal heat by reflex action. As section of the 

 sympathetic filaments increases the heat in particular parts, 

 with an increase in the supply of blood, and their galvaniza- 



1 See vol. iii., Secretion, p. 32. 2 See page 229. 



3 See vol. iii., Nutrition, p. 416. 



