ON THE ORGANIC FUNCTIONS. 471 



cited through the Cerebro-Spinal system ; whilst those of the contractile tis- 

 sues of the Viscera ( 234) are probably excited through nerves, which, 

 though connected with the Cerebro-Spinal system, act under peculiar condi- 

 tions, and are commonly spoken of as forming part of the Sympathetic 

 system. It has been shown ( 388 393) that all the contractile organs, 

 which may be excited through the Sympathetic or Visceral system of nerves, 

 may also be made to act by stimuli applied to the roots of the Spinal nerves; 

 but that each Cerebro-Spinal fibre appears to pass through several Ganglia, 

 before being distributed to the organs which it supplies. 



. Many speculations have been hazarded, as to the reasons why the Visceral nerves 

 are destitute of sensibility; and, at the time when the Sympathetic was supposed to be 

 merely an offset from the Cerebro-Spinal system, it was imagined that the use of the gan- 

 glia upon the roots of the spinal nerves was to " cut off sensation'' from those concerned in 

 the " vital and involuntary motions." The influence of Bichat's ingenious hypothesis, that 

 the Sympathetic system is complete and independent, ministering to the functions of Or- 

 ganic Life, as the Cerebro-Spinal does to those of Animal Life for a time caused this idea 

 to be abandoned. Since, however, it has been anatomically proved, that a large proportion 

 of the filaments of the visceral nerves are derived from the Spinal cord, this opinion has 

 been revived, in a somewhat modified form.* Nevertheless the evidence in its support is 

 somewhat vague ; especially if the truth of the doctrine formerly urged, that the Spinal 

 Cord is not itself a centre of sensation, be admitted. For it is only necessary to suppose, 

 that the white fibres of the Sympathetic nerve terminate in the true Spinal Cord, without 

 proceeding to the Brain, to have an explanation of the absence of sensory endowments in 

 the organs to which they are distributed, and of the complete removal of the muscles sup- 

 plied by their motor nerves, from voluntary control. That a few fibres, of which the actions 

 cannot be excited under ordinary circumstances, pass on to the Brain, would seem probable 

 from the fact of the sensibility of some parts, in disease, which are totally insensible in their 

 normal condition ; a fact in the explication of which, the hypothesis just alluded to affords 

 no assistance. 



622. It appears, then, that it may be stated as a general proposition, that 

 all the evident movements which can be excited, by irritation applied to one 

 part of the body, in the contractile organs or tissues of another, are really 

 effected through the true Spinal Cord ; whether the contractile .organ be a 

 powerful muscle, or a thin and feeble layer of fibres around a blood-vessel or 

 duct. Upon the reasons why the fibres of the Visceral nerves should be so 

 peculiarly separated from the rest, we can at present only speculate ; but it 

 may not be considered improbable that, by their peculiar plexiform arrange- 

 ment in the various ganglia through which they pass, connections are estab- 

 lished between remote organs, which tend to bring their actions into closer 

 relation with each other, than would otherwise be the case. The existence 

 of such connections for the purpose of harmonizing the several movements 

 of the Viscera, which are concerned in the various and complex operations of 

 Digestion and its attendant processes, may be inferred from the perfect con- 

 formity which exists between them, during all their different states of regular 

 action; and still more, perhaps, from the phenomena of their disordered con- 

 ditions. The study of these Sympathies is one of those departments of Phy- 

 siology, in which it maybe expected that much will be gained by patient and 

 well-directed investigation. 



623. The movements immediately concerned in the Organic Functions, how- 

 ever, are not influenced by Reflex action alone, but also by Emotional condi- 

 tions of the mind. This is most obvious in regard to the Heart. Every one 

 must have experienced the disturbance of its pulsations, consequent upon ex- 

 citement of the feelings, of almost any description. But other organs probably 

 experience similar changes, although of a less manifest character. It is well 

 known that the Sympathetic system is largely distributed upon the trunks of 



* See Dr. Alison on the Nerves of the Orbit; Edin. Phil. Trans., vol. xv.; and Med. Gaz. 

 vol. xxviii. p. 378. 



