100 PSYCHOLOGY. 



changes in delicate tlierniometers aud electric piles placed 

 against the scalp in human beings, and found that any intel- 

 lectual effort, such as computing, composing, reciting poetry 

 jsilently or aloud, and especially that emotional excitement 

 such as an anger lit, caused a general rise of temperature, 

 which rarely exceeded a degree Fahrenheit. The rise was 

 in most cases more marked in the middle region of the head 

 than elsewhere. Strange to say, it was greater in reciting 

 poetry silently than in reciting it aloud. Dr. Lombard's 

 explanation is that " in internal recitation an additional 

 portion of energy, which in recitation aloud was con- 

 verted into nervous and muscular force, now appears as 

 heat." * I should suggest rather, if we must have a theory, 

 that the surplus of heat in recitation to one's self is due to 

 inhibitory processes which are absent when we recite aloud. 

 In the chapter on the Will we shall see that the simple cen- 

 tral process is to speak when we think ; to think silently 

 involves a check in addition. In 1870 the indefatigable 

 Schiff took up the subject, experimenting on live dogs and 

 chickens, plunging thermo-electric needles into the sub- 

 stance of their brain, to eliminate possible errors from 

 vascula]' changes in the skin when the thermometers were 

 placed upon the scalp. After habituation was established, 

 he tested the animals with various sensations, tactile, optic, 

 olfactory, and auditory. He found ver^^ regularly an im- 

 mediate deflection of the galvanometer, indicating an abrupt 

 alteration of the intra-cerebral temjDerature. When, for in- 

 stance, he jDresented an empty roll of paper to the nose of 

 his dog as it lay motionless, there was a small deflection, 

 but when a piece of meat was in the paper the deflection 

 was much greater. Schift' concluded from these aud other 

 experiments that sensorial activity heats the brain-tissue, 

 but he did not try to localize the increment of heat beyond 

 finding that it was in both hemispheres, whatever might be 

 the sensation applied, t Dr. K W. Amidon in 1880 made 

 a farther step forward, in localizing the heat produced by 

 voluntary muscular contractions. Applying a number of 



* Loc. cit. p. 195. 



■{• The most convenient account of Scbiff's expeiiments is hy Prof. 

 Herzen, in the Revue Pbilosophique, vol. iii. p. 36. 



