48 BULLETIN OF THE UNIVERSITY OP WISCONSIN. 



These phenomena are easily observable in psychological ex- 

 periments, wherein it is possible to show that w T hen a subject 

 exerts his mind in the effort to solve a difficult problem, for 

 example, the volume of blood in the cerebral locality increases. 

 It was the physiologist, Angelo Mosso, 1 I believe, who first di- 

 rected the attention of scientists to this in his investigations 

 with the plethysmography And he was able to demonstrate the 

 same phenomenon also in another experiment. A subject is 

 placed upon a delicately constructed balance which remains 

 horizontal while he is in a condition of mental repose; but 

 when he is summoned to severe intellectual effort, or when 

 any lively emotion is aroused, the balance tips in the direc- 

 tion of the head, showing that the blood is surging brain- 

 ward and so of course away from the limbs. The increase in 

 temperature during mental activity has been studied by Lom- 

 bard, Schiff, and others by means of the thermo-electric needle 

 plunged into the brains of dogs and other animals. 2 When 

 in this latter case any sense was stimulated, as smell, the nee- 

 dle if placed in the olfactory region of the brain would show 

 that heat was being liberated. 



The significance of these well-known but yet little appreciated 

 phenomena becomes apparent when they are interpreted in 

 view of the accepted explanations of similar phenomena occur- 

 ring during muscular exertion. It is a simple physiological 

 fact that the blood supply in a muscle is greater during activity 

 than while at rest, caused by the necessity of removing and 

 repairing the increased waste produced by the degradation of 



1 Reference is made to this phenomenon in Mosso's Fear, p. 68. The subject 

 is treated in detail with respect to methods of investigation, and results in Die 

 Ermiiding, pp. 195 et seq. There is a very good r6sum§ of recent investigation 

 relating to the effect upon circulation of intellectual and emotional activity, to- 

 gether with the presentation of results of original researches, in the Psycholog- 

 ical Review for January, 1899, by Angell and Thompson, — The Relation between 

 Certain Organic Processes and Consciousness. 



A. Binet and V. Henri in La Fatigue Intellectuelle, pp. 81 et seq., recognize 

 that intellectual activity produces dilation of the cerebrum, but they do not 

 attach so great importance to this phenomenon as many do. Their discussion 

 does not bear directly upon the problem involved here, however. 



2 See Pedagogical Seminary, loc. cit. 



