ru DISEASES Class III. 2. i. i. 



ftimulus of vinous fpirit ; which may properly be termed irrita- 

 tive paralyfis of thofe parts of the fyftem.. 



In the fame manner in common palfies the inaction of the 

 paralytic mufcle feems not to be owing to defect of the ftimu- 

 lus of the will, but to exhauftion of fenforial power. Whence 

 it frequently follows great exertion, as in Seel:. XXXIV. 1. 7. 

 Thus Some parts of the Syftem may ceafe to obey the will, as in 

 common paralyfis •, others may ceafe to be obedient to fenfation, 

 as in the impotency of age ; others to irritation, as in fchirrous 

 vifcera ; and others to allbciation, as in impediment of fpeech ; 

 yet though all thefe may become inexcitable, or dead, in reSpedt 

 to that kind of ftimulus, which has previoufly exhaufted them, 

 whether of volition, or fenfation, or irritation, or aflbciation, 

 they may ftill in many cafes be excited by the others. 



SPECIES. 



1 . LaJJltudo. Fatigue or wearinefs after much voluntary ex- 

 ertion. From the too great expenditure of fenforial power the 

 mufcles are with difficulty brought again into voluntary con- 

 traction ; and feem to require a greater quantity or energy of vo- 

 lition for this purpofe. At the fame time they ftill remain obe- 

 dient to the fHmulus of agreeable fenfation, as appears in tired 

 dancers finding a renovation of their aptitude to motion on the 

 acquifition of an agreeable partner ; or from a tired child riding 

 on a gold-headed cane, as in Sect. XXXIV. 2. 6. Thefe muf- 

 cles are likewiSe ftill obedient to the fenforial power of aflbcia- 

 tion, becaufe the motions when thus excited, are performed in 

 their defigned directions, and are not broken into variety of ges- 

 ticulation, as in St. Vitus's dance. 



A laftitude likewife frequently occurs with yawning at the 

 beginning of ague-fits ; where the production of fenforial pow- 

 er 111 the brain is lefs than its expenditure. For in this cafe the 

 torpor may either originate in the brain, or the torpor of fome 

 diftant parts of the fyftem may by Sympathy afFecl: the brain, 

 though in a lefs proportionate degree than the parts primarily 

 affected'. 



2. Vaciliatio fenilis. Some elderly people acquire a fee-faw 

 motion of their bodies from one fide to the other, as they fit, 

 like the ofcillation of a pendulum. By thefe motions the mut- 

 cles, which preferve the perpendicularity of the body, are alter- 

 nately quiefcent, and exerted ; and are thus lefs liable to fatigue 

 or exhauftion. This therefore refembies the tremors of old 

 people above mentioned, and not thefe fpafmodic movements of 

 the face or limbs, which are called tricks, defcribed in Clafs IV. 



