870 INFLUENCE OF THE NERVOUS SYSTEM 



erection, if the mind be possessed with any feeling of doubt or apprehension 

 as to the existence of the sexual ability. The muscular walls of the Ali- 

 mentary canal seem frequently to be excited to increased action by agitating 

 emotions; but it may be doubted how far this is a primary effect of the 

 mental state, or how far it is consequent upon the influence of that state upon 

 the Secretions poured into the canal ( 725). The influence of the state of 

 expectant attention, as of the emotions, is strongly manifested in the case of 

 the Heart; the action of which, as Sir H. Holland has remarked, "is often 

 quickened or otherwise disturbed by the mere centring the consciousness 

 upon it, without any emotion or anxiety. On occasions where its beats are 

 audible, observation will give proof of this, or the physician can very often 

 infer it while feeling the pulse; and where there is liability to irregular 

 pulsation, such action is seemingly brought on, or increased, by the effort of 

 attention, even though no obvious emotion be present." 1 There can be no 

 doubt that the movements of the lower part of the Alimentary Canal are 

 capable of being affected in a similar manner ; since we may frequently trace 

 the rapid descent of the fecal mass into the rectum, when we expect to be 

 shortly able to discharge it ; and it is in great part in this mode, that habit 

 operates in producing a readiness for defecation at particular times, and that 

 bread-pills and other supposititious purgatives unload the bowels. 2 



718. Trophic Nerves. The existence of a special system of nerves possess- 

 ing a direct influence on the process of nutrition, though suggested by other 

 writers, was first clearly enunciated by Samuel of Leipsic, and has been so 

 warmly supported by Ducheune, that he has declared that " if trophic nerves 

 did not exist, it would be necessary to invent them." The positive facts 

 which have led to their admission are, however, comparatively few, and in 

 fact may almost be considered as limited to the single one, demonstrated by 

 Luclwig, that certain glands can be excited to action by the stimulation of 

 their nerves independently of their blood supply. (Saliva, 105.) The 

 view taken by Samuel 3 is that the so-called trophic nerves arise from the 

 ganglia on the posterior roots of the spinal nerves and run centrifugally to 



1 Chapters on Mental Physiology, p. 16. 



Tin- Author may mention the two following CUSPS, which have fallen within his 

 own knowledge, as curious illustrations of the influent-oof mental state* upon the 

 movements of the alimentary canal. The first of these occurred in the person of a 

 literary man. of a somewhat hypochondriacal temperament, who had been troubled 

 with continued costive-ness, for which he had been accustomed to take an aperient 

 pill daily. Finding that this ceased to have its usual effect, and being tearful of 

 increasing his regular dose, he applied for advice to a practitioner, who, having had 

 former experience of what Mental agency alone would do, determined to try it> effect 

 in this instance. Seating his patient before him, with the abdomen uncovered, he 

 desired him to fix his attention intently upon his abdominal sensations, and assured 

 him that in a short time he was quite certain that he would begin to feel a movement 

 in his bowel-, which would end in a copious evacuation. He himself did nothing 

 but look steadily at his patient, with an air of great determination and confidence, 

 and point his finger at the abdomen, moving it along the arch of the colon, and (as 

 it were) in the course; of the convolutions of the small intestines, so as to aid the 

 patient in fixing his attention upon them. In a short time the expected movements 

 were felt, and a copious evacuation soon followed; and for some time afterwards, the 

 bowels eontinued to act freely without medicine. In the other case, a Lecturer at a 

 publi" I limitation was seized with a strong impulse to defecation during his lecture; 

 and was greatly inconvenienced by the effort necessary to restrain it. Before every 

 subsequent lecture in the same place, the same impulse returned upon him, notwith- 

 standing that he might have previously unloaded his bowels elsewhere. In this case, 

 then- wa* obviously a state of apprehension combined with the simple anticipation ; 

 but the intluence of the latter is shown by the fact, that in no other place did this 

 individual experience the impulse in question under the like circumstam < -. 



3 Die trophische Nervcn, IHiiU. 



