184 OF. THE VOLUNTARY MOTIONS. 



There is no question that the pulsation of the heart 

 and arteries may be accelerated or retarded by the 

 varied state of respiration.* 



Rumination shews that the action of the stomach may 

 be voluntary, and I myself once distinctly found it so, 

 in a man who had the power of ruminating. 



Although the motion of the iris is involuntary in most 

 persons, I have been credibly informed that some have 

 been able, by a considerable effort, to subject it to the 

 will and contract the pupil in a weak light. 



So numerous are the motions commonly called in- 

 voluntary which become voluntary in some particular 

 individuals, especially if aided by attention and live- 

 liness of imagination^ 



Thus I have seen some able to produce at any time 

 a spasmodic horripilation of the skin, by representing 

 some unpleasant sensation to their imagination. 



Others have had the power of exciting local sweat in 

 the hands, &c. $ (A) 



288. This may perhaps bo explained on the principle 

 of sensorial reaction, (50) which may be produced by 

 imagination — a mental stimulus, as easily as by a cor- 

 poreal stimulus acting upon the sensorium. (52) Many 

 phenomena accord admirably with this explanation; 

 v. c. the various causes of the erection of the penis, 

 and of the flow of saliva. 



N • See Sam. Lath. Mitchill, On the gaseous uyd of azote, &c. New York 

 1795. 12nio. p. 26. 



Also Loop. Caldani, Memorie delta accademia di Man tor a. T. i. 1795. p. 1 18. 



+ See the liapport des Commissairrs charge's par le Roy de Cexamen du 

 magne'tisrne animal, written by J. Sylv. Bully, a man worthy of a better fate. 

 Paris. 1784. 4to. p. 16. 



J See r. c. T. Bartholin, Act. Hafmetu. 1676. vol. i*. p. 191, 



