(II. III.] ACTIONS OF THE UNDERSTANDING. 177 



although we do not see their connection,, nor recognise them as 

 the results of sentient actions (141). Fourthly, since the vital 

 spirits are necessary for all animal functions, and consequently 

 to the production of the material ideas of intellectual concep- 

 tions (15), and since long and deep thought may waste or 

 destroy them (20), and thus the free action of the other animal 

 forces be restricted (22), it follows that in this way the con- 

 ceptions of the understanding may act powerfully in the animal 

 economy. Lastly, since they certainly develop some actions 

 in the body through the nerves, partly, as internal sensations, 

 (or as sensational incitements,) in so far as they are pleasing 

 or unpleasing (80), partly, because they are commingled each 

 time with sensational elements, it cannot be matter for sur- 

 prise, that many and important changes are produced in the 

 body by the exercise of the intellect, although the intellectual 

 conceptions, purely as such, do not act directly on the nerves. 

 (Compare §§136—141.) 



332. The corporeal phenomena which are manifestly the 

 results of the effort of the intellect must be investigated on 

 these principles. By deep and intense thought, the body 

 wastes, the muscles become weaker, the blood is determined 

 to the head, the extremities become cold; the blood is 

 changed in composition, the sensational property of the nerves 

 is altered, and they become too sensitive, and excite irregular 

 sentient actions, which derange the sentient action of the 

 other sensational conceptive forces: the functions of the viscera 

 are irregularly performed, and in particular the digestion is 

 much impaired. Hence it follows, that deep studies and scien- 

 tific pursuits are not the natural objects of man, but opposed 

 to his health and well-being. Thus it is, that those learned 

 men who cultivate the abstract sciences are generally feeble, 

 meagre, sensitive, splenetic, hypochondriacal, and fanciful, and 

 have impaired digestion. On the contrary, the strongest and 

 healthiest men, with good digestion, are little given to study 

 the abstract sciences, and little capable of comprehending them. 

 These principles have an important bearing on pathology. 



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