SYMPATHETIC SYSTEM OF NERVES. 373 



of ganglia (c, fig. 191), that seem to belong to the same system. 

 The nerves proceeding from this system, which is called the 

 Sympathetic, are distributed, not like those of the cerebro- 

 spinal, to the skin and muscles, but to the organs of digestion 

 and secretion, and to the heart and blood-vessels. Hence the 

 former system of nerves, being that by which sensations are 

 received and spontaneous motions executed, is called the 

 nervous system of animal life ; whilst the latter, being con- 

 nected with the nutritive processes alone, is termed the nervous 

 system of organic life. 



462. What is the nature of the influence which the Sympa- 

 thetic system exerts over the functions of the parts to which 

 it is distributed, is not yet clearly made out. The sympathetic 

 nerves distributed to the alimentary canal have been ascer- 

 tained to have the power of exciting its peristaltic actions ; 

 and those which are distributed with the blood-vessels (on the 

 coats of which they form a minute net- work) have a direct influ- 

 ence over their calibre, producing changes in the local circulation 

 in obedience to passions and emotions of the mind, as well as 

 to states of other bodily organs. Of this influence we have a 

 familiar example in the acts of blushing and turning pale from 

 agitation of the feelings, and a more decided but less frequent 

 one in the fainting which sometimes occurs from a sudden 

 shock. It is doubtful, however, whether the Sympathetic 

 system really possesses motor filaments of its own ; its motor 

 actions being certainly in part dependent upon filaments de- 

 rived from the cerebro-spinal system. The action of its motor 

 fibres upon the muscular coats of the blood-vessels supplying 

 the glands, serves to regulate the quantity of the fluids secreted 

 by these organs, especially in cases in which the demand for 

 the secretion is intermittent; but as there is evidence that 

 the quality of many secretions may be affected by mental states 

 ( 353), it seems likely that the fibres peculiar to the Sympa- 

 thetic system ( 60) may be the channel of this influence. 

 Although it is still impossible to define precisely the functions 

 of the Sympathetic system, yet it may be stated generally, 

 that in virtue of the two modes of action just explained, it 

 seems to harmonise and blend together the various actions of 

 Nutrition, Secretion, &c., in such a manner as to bring them 

 into conformity with each other, and with the condition of 

 the organs of Animal life. 



