REFLEX SYMPATHETIC MOVEMENTS. 311 



irritant substances into the alimentary canal, and from the irritation 

 of teething in infants. In the foregoing cases, it would seem that the 

 fibres of the sympathetic system play an afferent part as regards the 

 stimuli employed ; and that the effects of the stimuli are conveyed to 

 the reflex centre of the spinal cord, and thence act upon efferent fibres 

 belonging to the cerebro-spinal system. But, in the second place, 

 examples of reflex acts, performed through the sympathetic, quite in- 

 dependently of the cerebro-spinal system, are found in the case of 

 those movements of the intestines, or of the heart, which continue 

 after the trunks of their nerves are divided, or even after they have 

 been entirely removed from the body. The apparatus through which 

 the movement in such cases is excited must be the sympathetic ner- 

 vous system. When, indeed, a stimulus is applied, under such cir- 

 cumstances, to a part of the intestine, or to a portion of the heart, 

 the movement produced is not merely local, but is transmitted, or prop- 

 agated, to neighboring parts ; and, instead of producing only a sin- 

 gle motion, as would be the case in a detached voluntary muscle, the 

 movement is continued, and even follows the ordinary peristaltic or 

 rhythmic .character. The centres, through which the effects of the 

 stimulus are thus extended beyond the immediate seat of their appli- 

 cation, are the intrinsic or visceral ganglia, to and from which affer- 

 ent and efferent fibres convey the effects of the stimulus, in the ordi- 

 nary reflex manner. According to another view, these ganglia, during 

 life, are the centres of a direct governing force, which regulates the 

 movements of the parts, that is to say, a central stimulus originates in 

 them, independently of the effects of stimuli conveyed to them by 

 afferent fibres. The details of this subject will be found in the Sec- 

 tions on Digestion and Circulation, in the account of the movements 

 of the heart and the intestines, and of their dependence on the nervous 

 system. 



As already stated, the movements of the heart and intestines, 

 whether performed by reflex actions, governed through the sympa- 

 thetic system, or by the action of direct centric stimuli, originating in 

 the sympathetic system, and entirely beyond the control of the will, 

 may be affected through the cerebro-spinal system, by exciting or de- 

 pressing ideas and emotions. Lastly, experiments show that the sym- 

 pathetic is so far dependent on the cerebro-spinal axis, that stimula- 

 tion of certain parts of the brain excites movements in the muscles of 

 vegetative life; and that, after destruction of brain and cord, the 

 general sensori-motor functions of the sympathetic are lost. 



Influence of the Nervous System on Nutrition and Secretion. 



There is abundant evidence, which will be hereafter detailed in the 

 Sections on the above-named subjects, to show that the processes of 

 nutrition and secretion can be influenced through the nervous system. 

 There is reason to believe that the part of the nervous system here 

 specially concerned, is the sympathetic nervous system, experiments 

 having shown that when the sympathetic nerves, supplying a part of 

 the body, are divided, the nutrition of that part is immediately inter- 



