866 INFLUENCE OF THE NERVOUS SYSTEM 



tern) must be distributed along with the branches proceeding from the trunks 

 which they help to form ; as must also a part of those fibres which are sent 

 from the proper Sympathetic ganglia into the roots of the same nerves, a 

 large part of them, however, being distributed upon the bloodvessels of the 

 Spinal Cord itself. 



713. If, then, it be inquired what inferences we are entitled to draw 

 respecting the functions of the Sympathetic system of nerves, from our 

 knowledge of its Anatomical distribution, we are at once justified in reply- 

 ing that the muscular tissue which directly enters into the formation of the 

 vessels, and especially of the smaller arteries, is supplied essentially from 

 this source. In accordance with this, it is found that excitation of the sym- 

 pathetic nervous ganglia, whether by direct or reflex irritation, leads to con- 

 traction of the vessels, and consequent diminution in the activity of all 

 organic processes, such as secretion, nutrition, growth, and development; 

 their paralysis, as is well seen in cases of section of the cervical sympathetic, 

 disclosing itself by the establishment of the opposite conditions. Again, it 

 is certain that a large proportion of the Muscular apparatus which directly 

 ministers to the Organic functions, that, namely, which surrounds the ali- 

 mentary canal from the stomach downwards, with the gland-ducts which 

 open into it, and that, also, which forms the walls of the bladder and uterus, 

 of ureters and Fallopian tubes receives no other nervous supply ; and, con- 

 sequently, that of whatever motor influence these parts may receive from 

 Mental states or from excitation not applied to themselves, this system of 

 nerves must be the channel. The same may be said, too, in regard to that 

 greater portion of the Glandular apparatus, which is exclusively supplied by 

 the Sympathetic nerve, and chiefly by the plexuses that embrace its blood- 

 vessels; since any such alterations in its rate of activity, or in the charac- 

 ter of its products, as depend upon conditions of Mind, can be brought about 

 through no other instrumentality. It is not a little remarkable, however, 

 that those portions of the Muscular apparatus of Organic lite, which most 

 obviously exhibit in their action the influence of the Nervous system, both 

 in their respondence to emotional states and in their "sympathy" with dis- 

 turbance in other functions, namely, the Heart and the Stomach, derive 

 a considerable part of their nervous supply directly from the Cerebro-spinal 

 system. And it is still more significant, that most of those Glands whose 

 function is occasional, and whose states of activity are most obviously influ- 

 enced by affections of the Mind, are specially supplied by Cerebro-spinal 

 nerves, in addition to the Sympathetic plexuses which they receive on the 

 walls of their bloodvessels: thus, the Lachrymal and Salivary glands are 

 supplied with branches of the Filth and Facial nerves; and the Mammary 

 glands by branches of the Intercostals. It cannot but be deemed highly 

 probable, then, from this circumstance alone, that the influence of mental 

 states upon the function of Secretion may be exerted through the nerves of 

 the Cerebro-spinal system, as well as through those of the Sympathetic. 



714. It must be in virtue of the connections of the Sympathetic with the 

 Cerebro-spinal system, that the parts which are solely supplied with nerves 

 from the former, are capable of transmitting,sensory impressions to the Sen- 

 sorium. It is true, that, under ordinary circumstances, these parts are in- 

 sensible : that is, impressions made upon them do not travel onwards through 

 the Spinal Cord to the Encephalon ; but their sensibility is acutely mani- 

 fested in morbid states, in which the impressions seem to be propagated 

 further than usual, in virtue of their greater potency. That it is the office 

 of the ganglia on the roots of the Spinal nerves to "cut off" sensation," that 

 is, to prevent the further transmission of sensory impressions, is an old doc- 

 trine; and there seems much reason to believe that this may be effected by 



