No. 7.] AMERICAN ASSOCIATION. 389 



that of copper, the fact that the energy of nerve moves at the 

 rate of only twenty- eight metres per second is really no proof 

 that it is not electricity. 



Of the '^ physical aspects of the mind-question," Professor 

 Barker says : 



" The problem of the quantitative changes which take place 

 in the organism is a very curious and interesting one. That 

 the energy of the brain comes from the food will be disputed by 

 no one in these days. Hence, the brain must act like a machine 

 and transform energy. There is then a purely physiological re- 

 presentation of mental action, concerned with forces which are 

 known and measurable. The researches of Lombard long ago 

 showed the concomitant heat of mental action. Recent researches 

 are equally interesting, which show that mental operations are 

 not instantaneous but require a distinct time for their perform- 

 ance. By accurate chronographic measurement, Hirsch has 

 shown that an irritation on the head is answered by a signal 

 with the hand only after one-seventh of a second ; that a sound 

 on the ear is indicated by the hand in one-sixth of a second ; 

 and that when light irritates the eye, one-fifth of a second 

 elapses before the hand moves." 



• ••••••«#••* 



" Another important fact concerning nervous action is that 

 its amount may be measured by the quantity of blood consumed 

 in its performance. Dr. Mosso of Turin has devised an ap- 

 paratus called the Plethysmograph — drawings of which were 

 exhibited at the London Apparatus Exhibition of 1876 — designed 

 for measuring the volume of an organ. The fore-arm, for 

 example, being the organ to be experimented on, is placed in a 

 cylinder of water and tightly enclosed. A rubber tube connects 

 the interior of the cylinder with the recording apparatus. With 

 the electric circuit by which the stimulus was applied to produce 

 contraction, were two keys, one of which was a dummy. It was 

 noticed that, after using the active key several times, producing 

 varying current strengths, the curve sank as before on pressing 

 down the inactive key. Since no real effect was produced, the 

 result was caused solely by the imagination, blood passed from 

 the body to the brain in the act. To test further the effect of 

 mental action, Dr. Pagliani, whose arm was in the apparatus, 

 was requested to multiply 267 by 8, mentally, and to make a 

 sign when he had finished. The recorded curve showed very 



