98 PSYCHOLOGY. 



graph ' as au indicator, discovered that the blood-supply to 

 the arms diminished during intellectual activity, and found 

 furtliermore that the arterial tension (as shown by the 

 sphygniograph) was increased in these members (see 



Fig. 23.— Sphymographic pulse-tracing. A, during intellectual repose ; B, during in- 

 tellectual activity. (Mosso.J 



Fig. 23). So slight an emotion as that produced by the 

 entrance of Professor Ludwig into the laboratory was in- 

 stantly followed by a shrinkage of the arms.* The brain 

 itself is an excessively vascular organ, a sponge full of 

 blood, in fact ; and another of Mosso's inventions showed 

 that when less blood went to the arms, more went to the 

 head. The subject to be observed lay on a delicately bal- 

 anced table which could tip downward either at the head 

 or at the foot if the weight of either end w^ere increased. 

 The moment emotional or intellectual activity began in the 

 subject, down went the balance at the head-end, in conse- 

 quence of the redistribution of blood in his system. But 

 the best proof of the immediate afflux of blood to the brain 

 during mental activity is due to Mosso's observations on 

 three persons whose brain had been laid bare by lesion of 

 the skull. By means of apparatus described in his book, f 

 this physiologist was enabled to let the brain-pulse record 

 itself dii ectly by a tracing. The intra-cranial blood-pressure 

 rose immediately w'henever the subject was spoken to, or 

 when he began to think actively, as in solving a problem in 

 mental arithmetic. Mosso gives in his work a large num- 

 ber of reproductions of tracings which show the instanta- 

 neity of the change of blood-supply, whenever the mental 

 activity was quickened by any cause Avhatever, intellectual 



* La Panra(18S4), p. 117. 



t Ueber den Kreislauf des Blutes im menscblichen Gehirn (1881).. 

 chap. II. The Introduction gives the history of our previous knowledge 

 of the subject. 



