ON MUSCULAR MOTION. g^3 



-animal feelings eventually urge the refpiratory raoveraents in 

 lefpight of the will. Thefe lafl: mufcles appear to have be- 

 come automatic by the continuance of habit. 



The afes of voluntary mufcles are attained by experience, Voluntary ac- 

 imitation, and inftrudion : but fome of them are never called ^'?"^ require 



education j the 

 into adion among Europeans, as the mufcles of the external involuntary are 



ears, and generally the occipilo-frontah's. The purely invo- ""[^"^ ^'' '^^" 

 luntary mufcles are each aded upon by different fubtlances, 

 which appear to be their peculiar ilimuli ; and thefe ftimuli 

 co-operate with the fenforial influence in producing their con- 

 tractions ; for example, the bile appears to be the appropriate 

 flimulus of the mufcular fibres of the alimentary canal below 

 the ftomach, becaufe the abfence of it renders thofe paflages 

 torpid. The digetled aliment, or perhaps the gaftric juice in a 

 certain flate, excites the ftomach. The blood Simulates the 

 heart/ light the iris of the eye, and mechanical preffure feems 

 to excite the mufcles of the oefophagus. The lafl caufe may 

 perhaps be illuflrated by the infiances of compreffion upon 

 the voluntary mufcles, when partially contracted, of which, 

 there are many familiar examples. Probably the mufcles of 

 the officula auditus are awakened by the tremors of found ; 

 and this may be the occafion of the peculiar arrangement ob- 

 fervable in the chorda tympani, which ferves thofe mufcles. 



Thefe extraneous ftimuli feem only to a6l in conjunction Stimuli feem to 



with the fenforial power, derived by thofe mufcles from the ^^^^'^^ fenfonal 



... , r 1 rr r , • i i . powcr in lome 



gangliated nerves, becaule the pallions ot the mmd alter the refpeft refem- 



mufcular aClions of the heart, the alimentary canal, the refpi- ^^'"S <^he paf- 

 ratory mufcles, and the iris; fo that probably (he refpeCJive * 

 ftimuli already enumerated, only ad fubfervienlly, by awak- 

 ening the attention of the fenforial power, {if that expreffion 

 may be allowed,) and thereby calling forth the nervous in- 

 fluence, which, from the peculiar organization of the great 

 chain of fympathetic nerves, is effecled without confcioufnefs : 

 for, when the attention of the mind, or the more interefling 

 palTions prevail, all the involuntary mufcles aCl irregularly, 

 and unfteadily, or wholly ceafe. The movements of the iris 

 of the common parrot is a flriking example of the mixed in- 

 fluence. 



The muCcles of the lower tribes of animals, which are often Lower tribes of 

 entirely fupplied by nerves coming from ganglions, appear of ^^'^a's aft by 

 ,. , r , , .1 • 1 *• • • II external excite- 



tljis clafs J and thus the animal motions are principally regu- ^jgnts. 



lated 



