SEGT. XII. 2. i. AND EXERTION. 53 



and the quantity of fenforial power, or fpirit of animation, re- 

 dding in the contracting fibres. Where both thefe quantities 

 are great Jlrength is produced, when that word is applied to the 

 motions of animal bodies. Where either of them is deficient, 

 lueahiefs is procured, as applied to the motions of animal bodies. 



Now as the ienforial power, or fpirit of animation, is perpet- 

 ually exhaufted by the expenditure of it in fibrous contractions, 

 and is perpetually renewed by the fecretion or production of it 

 in the brain and fpinal marrow, the quantity of animal ftrength 

 muft be in a perpetual date of fluctuation on this account ; and 

 if to this be added rhe unceafing variarion of all the four kinds 

 of ftimuius above defcribed, which produce the exertions of the 

 fenforial powers, the ceafelefs viciflitude of animal ftrength be- 

 comes eafiiy comprehended. 



If the quantity of fenforial power remains the fame, and the 

 quantity of ftimuius be lefiened, a weaknefs of the fibrous con- 

 traction 1 ersfues, which may be denominated debility from defeEl 

 efjiirnuius. If the quantity of ftimuius remains the fame, and 

 the quantity of fenforial power be leifened, another kind of 

 M viicfs eirues, u hich may be termed debility from defect offen- 

 povi-er ; the former of thefe is called by Dr. Brown, in 

 i. , Elements of Medicine, direct debility, and the latter Indi- 

 ra ; debili y The coincidence of fome parts of this work with 

 correlpondent deductions in the Brunonian Elementa Medi- 

 cinse ; a work (with fome exceptions) of great genius, muft be 

 confidered as confirmations of the truth of the theory, as they 

 were probably arrived at by different trains of reafoning. 



Thus in thofe who have been expofed to cold and hunger 

 there is a deficiency of ftimuius. While in nervous fever there 

 is a deficiency of fenforial power. And in habitual drunkards, 

 in a morning before their ulual potation, there is a deficiency 

 both of ftimuius and of fenforial power. While, on the other 

 hand, in the beginning of intoxication there is an excefs of ftim- 

 uius ; in the hot-ach, after the hands have been immerfed in 

 fnow there is a redundancy of fenforial power ; and in inflam- 

 ma'ory difeafes with arterial ftrength, there is an excefs of both. 



Hence if the ienforial power be leffened, while the quantity 

 of ftimuius remains the fame, as in nervous fever, the frequen- 

 cy of repetition of the arterial contractions may continue, but 

 their force in refpect to removing obftacles, as in promoting the 

 circulation of the blood, or the velocity of each contraction, 

 will be diminifhed, that is, the animal ftrength will be leflened. 

 And fecoridly, if the quantity of fenforial power be leiTened, and 

 the ftimuius be increased to a certain degree, as in giving opium 



in 



