SYMPATHETIC SYSTEM OP 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. 
