Scientific Lectures. 245 



made of bismuth, the other of an alloy of antimonj and zinc. - Pre- 

 liminary trials having shown that any change of temperature within 

 the skull was soonest manifested externally in that depression which 

 exists just above the occipital protuberance, a pair of these little bars 

 was fastened to tlie head at this point ; and to neutralize the results 

 of a general rise of temperature over the whole body, a second pair, 

 reversed in direction, was attaclied to the leg or arm, s(.> that if a like 

 increase of heat came to l)oth, the electricity developed by one would 

 be neutralized by the other, and no effect 1)0 produced upon the 

 needle unless only one was affected. By long practice it was 

 ascertained that a state of mental torpor could be induced, 

 lasting for hours, in which the needle remained stationary. But let 

 a person knock on the door outside the room, or speak a single 

 AViird, even though the experimenter remained absolutely pas- 

 sive, and the reception of the intelligence caused the needle to swing 

 through twenty degrees. f In explanation of this production of 

 heat, the analogy of the muscle at once suggests itself. Xo conver- 

 sion of energy is complete ; and as the heat of muscular action rep- 

 resents force which has escaped con\'ersion into motion, so the heat 

 evolved duj-ing the reception of an idea, is energy which has escaped 

 conversion into th()ught, from precisely the same cause. Moreover, 

 these experiments have shown that ideas wliich affect the emotions, 

 produce most heat in their reception ; " a few niinutes' recitation to 

 one's self of eniotioiud poetry, producing more eflect than several 

 hours of deep thought.'' Ileuce it is evident that the mechanism 

 for the production of deep thought, accomplishes this conversion of 

 energy fiir more perfectly than that which produces simply emotion. 

 But we may take a step further in this same direction. A muscle, 

 precisely as the hiw of correlation requires, develops less heat when 

 doing work than when it contracts without doing it. Suppose, now, 

 that beside the simple reception of an idea by tlie brain, the 

 thought is expressed outwardl.y by some muscular sign. The con- 

 version now takes two directions, and in addition to the })roductiou 

 of thought, a portion of the enei-gy a[)pears as nerve and muscle- 

 power ; less, therefore, should appear as heat, according to our law 

 of correlation. Dr. Lombard's experiments have shown that the 

 amount of heat developed by the recitation to one's self of emo- 



* The apparatus employed is illustratpd and fully described in Urowii-Sequard's Archives de 

 Phyaiologie, i, 499, June, 1S08. By it the l-4(W0tli of a d(i<:ree. Centigrade, may be indicated. 



+ Lombard. J. S.. New Yorli State Medical Journal, v. 198, June, 1SG7. [A part of lhe«e facts were 

 communicated to me directly by their discoverer.] 



