49 



been carried off in this case, and how deep the impression must have been 

 in the palm of the hand, doubly affected by the cold, and by the vital re- 

 action, which terminated in inflammation ! I have produced a similar ef- 

 fect, by endeavouring to melt a piece of ice in my hand, during the heat 

 of summer. In this experiment, the impression of cold is soon succeed- 

 ed by a sensation of acute pain and extraordinary thr.obbings, in the hand 

 and fore arm. When the two hands are afterwards compared, that 

 which held the piece of ice is extremely red, from the congestion of 

 blood in the cutaneous capillary tissue, and is very different in its appear- 

 ance, from that which was not the subject of experiment. 



Analogous facts, if seriously considered, should induce the followers of 

 Brown to apply to the effects of cold, the distinction which he applied to 

 debility, of direct and indirect They would have no difficulty in ascer- 

 taining, that in its medical application, that negative state of caloric, 

 which is directly debilitating, may, nevertheless, by the re-action which 

 it excites, be considered as an indirect tonic. 



X. OF THE SYSTEM OF THE GREAT SYMPATHETIC 



NERVES*. 



The great sympathetic nerves are to be considered as the bond destin- 

 ed to unite the organs of the nutritive functions, by whose action man 

 grows, is evolved, and incessantly repairs the continual waste attending 

 the vital motions. They form a nervous system, very distinct from the 

 system of the cerebral nerves; and, as the latter are the instruments of 

 the functions by which we hold intercourse with external objects, the 

 great sympathetic nerves supply motion and life to the organs of the in- 

 ward, assimilating, or nutritive functions. 



In animals, without vertebrae, may not the nervous system, which floats 

 in the great cavities with the viscera which they contain, be considered 

 as consisting entirely of the great sympathetics ? t These nsrves are 

 principally distributed to the organs of inward life, whose activity, in 

 those animals, seems to grow, in proportion as their external senses, and 

 their faculty of locomotion, are imperfect. If the great sympathies exist 

 in all the animals which have a distinct nervous system, do they not, in 



* See APPENDIX, Note H. 



j- TREVIRANUS, in his Biologie, considers the knotted cord found in the abdomen of 

 insects and worms to be the vertebral ganglia of the sympathetic nerve. That it can- 

 not be considered a spinal cord is evident : its situation sufficiently shows the difference. 

 The mollusca, and many animals removed a little above this class in the scale of crea- 

 tion, possess merely single ganglia, from which proceed fibrillae to the different organs. 

 The great sympathetic nerve is " the most general and the most original of all the 

 nerves." Its characters, are, however, modified in different classes. " In worms and 

 insects there are merely vertebral ganglia, without the coeliac ganglia of mammalia and 

 birds : in the acephalous mollusca there are the latter, without the former ; in the cut- 

 tle-fish and snails there are single ganglia of both kinds. " All these animals have no 

 spinal marrow ; fishes and reptiles have one, and also vertebral ganglia, but the cceliac 

 is not fully developed in them. (See the Observations of SERRES and WEBEE) as in birds 

 and mammalia. 



These remarks convey the sum of the observations made by those who have inquired 

 into the subject. How, therefore, can the ganglial class of nerves be considered to a* 

 rise from the cerebral and vertebral masses ? Copland. 



G 



