USEFUL PROJECTS. 



42^ 



activity cf the power of volition 

 produces the great difference be- 

 tween men and brates. 



vS". 12. treats of stimulus jsensoiial 

 exertion, and fdrous contraction. 

 The latter is Itrst considered. In 

 order to bring the particles of a 

 iBuscular fibre to ll at nearer ap- 

 proximation in which ifscnntraction 

 consists, some other agent is neces- 

 sary, which is the spirit of anima- 

 tion or sensorial power. After ani- 

 mal fibres have for some time been 

 t'xcited into contraction, a relaxa- 

 tion succeeds, even though the ex- 

 cilingcause continues to act. This 

 appears to be owing to an expendi- 

 ture or diminution of tiie spirit of 

 animation previously resident in the 

 fibres. It is succeeded, after a 

 certain interval, by a new contrac- 

 tion, and this interval is less in weak 

 than in strong subjects; which ac- 

 counts for the quick pulse in fevers 

 with debility ; )'et the contraction 

 itself is pciformed with more velo- 

 city in strong than in weak subjects. 

 After a fibre has been excited to 

 contraction, and the sensorial power 

 ceiises to act, the last situation or 

 configuration of it continues, unless 

 disturbed by some extraneous cause, 

 A contraction somewhat greater 

 than usual produces pleasuic ; one 

 still greater produces pain. As, in 

 every contraction of a fibre, there 

 js an expenditure of the spirit of 

 animation, increased action dimi- 

 nishes the propensity to activity ; on 

 theconfrary, less fibrous contraction 

 than usual causes an accumulation 

 of tlie spirit of animation, and in- 

 creased propensity to activity. 

 Hence the capability of being 

 excited to action is perpetually 

 Uuctualing. W hen much and per- 

 manently atjove or below the na- 

 tural standard, it becomes a disease. 



In sensorial exertion, three tilings 

 are to be observed ; the stimulus, 

 the sensorial power, and the con- 

 tractile fibre. An external stimului^ 

 first brings into action the faculty 

 called irritation, which causes con- 

 traction of the fibres, and this, if 

 perceived, produces pleasure or 

 pain J this is another stimulus, ca- 

 pable of causing conUaction by the 

 sensorial faculty, termed sensation j 

 or it introduces desire or aversion, 

 whicii excites another faculty term- 

 ed volition, which may act as ano- 

 ther stimulus 5 and, in conjunction 

 with all theae, the other sensorial 

 faculty, termed association, may be 

 called into action. The word sti- 

 inulus may therefore be properly 

 applied to any of the above four 

 causes exciting the four sensorial 

 powers into exertion; and the 

 quantity of motiou produced in any 

 part of the system will be as the 

 quantity of stimulus and the quan- 

 tity of sensorial powerresidingin the 

 fibres. AVhere these are great, 

 strength is produced; wiiere defi- 

 cient, jveahiess. If, the quantity 

 of sensorial power remaining the 

 same, that of stimulus be les- 

 sened, a weakness of contractions 

 ensues, which may be termed dehi- 

 lili/Jnm deject of stimulus ; if, the 

 quantity of stimulus remaining the 

 same, that of sensorial power be 

 If^s'.^ncd, del ility from diftct of senso- 

 rial poiter is the coDSiquencc. Ihe 

 former is the direct dtbilliy of Dr. 

 Brown; the lalttr, the indirect. 

 On these principles, with that of 

 the exhaustion of the spirit of ani- 

 mation by fibrous contractions, and 

 its renovation and accumulation on 

 quiescence, the phenomena of fe- 

 vers, and various other corporeal 

 afleciioiis, are developed, iome 

 remarks relative to medical practice 



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