( 128- ) 



If we take into consideration that even these single facts prove, 

 that every increase oi' the volume of the brain is attended bv quick 

 pulsations, we shall find that a great deal may be learned from 

 the study of the pulsation of the artery, when the brain is at work. 



This will be my first investigation. 



§ 3. The influence of the exertion of attention on the hearty 



the respiration and the extensor muscles of the hand 



and the neck. 



If we examine the influence which the exertion of attention has 

 on the heart and consider it separately for a moment, remarkable 

 facts will be found. 



First a few words about the arrangement of such experiments. 



As an example of a strong exertion of attention, which is very 

 slightly if at all attended by feelings of pain, the solving of a sum 

 is taken. The intellectual labour which is not attended by feelings 

 of pain or pleasure as suggested by the French authors is taken as 

 starting-point. The person used for the experiments is laid on a 

 couch. When he himself is perfectly calm and all around is quiet, 

 the pulse and the respiraton are registered. It has been arranged 

 that a number, generally of two figures, shall be called out to him 

 at a given moment, and that he shall continue to multiply this 

 number with itself, till a signal tells him to stop. He is to calculate 

 without using expedients. He works therefore with visual repre- 

 sentations, with remembrances of visual representations of numbers. 

 Generally tlie experiment lasts ± half a minute. 



The result, whether right or not right, is not pronounced by the 

 calculator; it must be dismissed at once from his mind. For many 

 experiments have proved, that the correctness or incorrectness of 

 the result is of no importance to my purpose; the rest or unrest 

 after the labour is. 



In such experiments the pulse and the respiration may be registered. 



The person to be experimented on lies caUnly, the cylinder rota- 

 tes quickly. Three levers note down. The pulsation of the arteria 

 radialis, the respiration and a tuningfork, which makes ten complete 

 vibrations a second, are registered with air-transport. The latter 

 enables us to read the time accurately down to the twentieth parts 

 of seconds, independent of the irregularities of the clockwork of the 

 cylinder. The tuning-fork is kept in continual vibration by an 

 electro-magnet. 



