OF THE FUNCTIONS OF THE GANGLIAL SYSTEM. jy 



17. From the manner in which the ganglial nerves invest the arteries proceeding 

 into the brain, and reasoning from analogy, we infer that they accompany the arteries 

 throughout the substance of this viscus, as in other organs of the body, and that they 

 influence its vascular functions in a similar manrier. 



18. The chief origin or centre of the ganglial system is generally situated, in all the 

 higher orders of animals especially, about the middle of the body, and, under the name 

 of the semilunar ganglion, it sends off branches, which form plexuses; these present 

 modified characters, as respects their external appearance and confirmation, in their 

 course to their different organs which they supply. 



This central ganglion more immediately supplies the organs of digestion, chylifac- 

 tion and circulation, where the expenditure of the vital Influence is greatest, and^sends 

 communicating branches to the subordinate ganglia and plexuses. 



19. The external characters of the ganglia and of their plexuses and ramifications 

 vary considerably in different situations, both as respects their colour, their external 

 form and internal structure. 



20. The subordinate ganglia, while they seem to receive a reinforcement of vital in- 

 fluence from the centre ganglion, modify that influence, and generate an accession to 

 it, suitable both in kind and degree to the functions of the organs which they are des- 

 tined to actuate. 



21. This class of nerves sends off, and receives cords of communication between the 

 brain and its subordinate organs, and between the spinal marrow and its distributions : 

 this seems to give rise to a reciprocal communication of influence between the organs 

 of nutrition, &.c. and those of relation, and a mutual dependence of function, which is 

 more intimate and apparent as we rise in the scale of creation, the independence 

 of the former class of functions becoming more evident as we descend, and the younger 

 the animal is as we ascend the scale. 



22. The extent and mode of communication between different parts of the volun- 

 tary nerves, and the ganglia and their distributions, vary very considerably. 



23. As this" class of nerves are so entirely different in their appearance, structure, 

 properties, and mode of distribution, and as they supply very different organs from 

 those which receive the encephalic class of nerves; so it maybe inferred that they 

 perform essentially different functions, although these functions, in the higher animals 

 more particularly, are in close relation with those of the rest of the body. 



24. As it is demonstrated, that the ganglial or vital nerves supply the heart, that 

 they surround and are ramified in the arteries throughout their distribution : that no 

 part of the vascular system receives, in a direct manner, any voluntary nerves ; and as 

 it is reasonable to suppose that this provision does not exist without accomplishing im- 

 portant purposes in the animal economy, ahd as the fibres of involuntary muscles are 

 evidently supplied from the same source ; and, farther, as we cannot suppose, conform- 

 ably to the laws of nature, that the bare coats of the vessels, and particularly of the 

 arteries, without such a provision, could be possessed of any vital properties so we in- 

 fer that all the vital phenomena, which the vascular system exhibits throughout the 

 body, are under the direct influence of this class of nerves. 



25. The distribution of these nerves around the arteries, and the manner in which 

 their nbrillze penetrate the coats of these vessels, seem to evince that they not only 

 impart to them whatever vital properties they may possess, but that they moreover pro- 

 duce those changes on the blood to which it" is subject, whilst flowing in the vessels, 

 and many of those phenomena which this fluid presents soon after it has been taken 

 from the body. 



26. It is also reasonable to suppose that the influence exerted by this system on the 

 capillaries, and the additional influence which its ramifications bestow on the substance 

 of the viscera, combine to produce the secretion, in secreting organs and surfaces, and 

 nutrition throughout the textures of the body. Hence, that the varied phenomena 

 displayed by the blood itself, by the functions of digestion, secretion*, assimilation, 



* No experiment instituted with the intention of showing the influence of the 

 nerves given off from the brain and spinal cord upon secretion, can prove the reality 

 of such influence. Because these orders of nerves are not ramified upon the vascular 

 system, nor do they even supply the capillary vessels. This is a wise provision ; for if 

 the heart and blood-vessels were directly under the influence of the voluntary nerves, 

 in any of its divisions, this system would be constantly deranged by it, and vascular 

 disease be incomparably more frequent and fatal, Such experiments, were they 

 instituted with thd*utmost precautions, could prove no more than has been shown bv 

 those of Dr. Phillips and Leirallois, which at most evince that the vital functions resul'- 



e 



