

cu. 1.] NERVE ACTIONS IN GENERAL. 191 



liines ; in the meanwhile it will be sufficient to prove its exist- 

 ce and reality by detailing a few of the most instructive and 

 most obvious facts. Thus, an external impression made on the 

 nerves of a portion of a muscle, or of the heart, or of the in- 

 testines separated from the body (as when, for example, the 

 outer or inner surface is burnt with acid, or pricked, or other- 

 wise irritated), excites the movements proper to the part, or 

 renews them for a time if they have already ceased, just as 

 when, in the natural condition of the animal, it was felt (167, 

 170). Thus, also, if immediately after decapitation, the body 

 be struck forcibly, the part struck becomes suffused with blood, 

 precisely as it would have been in the natural condition from 

 the external sensation of a blow (207). Thus, also, the glands 

 in an excised portion of intestine secrete on an external stimulus 

 being applied ; thus also the external impression of the gastric 

 juice, which in the natural condition excited the instinct of 

 hunger, stimulates the decapitated animal to rise up and seek 

 food, an act which is properly a sentient action of the instinct ; 

 thus, also decapitated insects allure with chirping wings to 

 sexual congress from the external irritations of the nerves of 

 their sexual organs ; thus, also, in decapitated butterflies, move- 

 ments necessary to copulation are excited, and the act itself 

 completed by the external stimuli proper to the instinct, while 

 decapitated female butterflies, flies, &c., are in the same way 

 excited to deposit their ova ; and thus, also the pinching of the 

 toe of a decapitated frog causes the same muscular contractions 

 and the same movements of the instinct of self-preservation, as 

 pain ordinarily excites in the natural condition. (Compare 

 Haller's ' Physiology,' § 402.) 



Note. — These facts (of which a great number may be found 

 scattered through the writings of observers) are stated here 

 without reference to authorities, being generally known and 

 undoubted. If further proofs be required by the reader, 

 especially as to the irritability of muscles, he is referred to the 

 works of Haller, Zimmerman, and Oeder, for it will be shown 

 subsequently, that the experiments which demonstrate the 

 irritability of a muscle, establish also that the animal motive 

 force of an external impression acts independently of the 

 cerebral forces (338). (Compare Haller's 'Opera Minora,^ 

 torn, i, pp. 368, seq.) 



