MODERN ASPECTS OF THE LIFE-QUESTION. 759 



may be measured by the quantity of blood consumed in its perform- 

 ance. Dr. Mosso, of Turin, has devised an apparatus called the ple- 

 thysmograph drawings of which were exhibited at the London Ap- 

 paratus Exhibition of 18TG designed for measuring the volume of an 

 organ. The forearm, for example, being the organ to be experimented 

 on, is placed in a cylinder of water and tightly inclosed. A rubber 

 tube connects the interior of the cylinder with the recording apparatus. 

 With the electric circuit, by which the stimulus was applied to pro- 

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

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

 ing 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 passing 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 2G7 by 8, 

 mentally, and to make a sign when he had finished. The recorded 

 curve showed very distinctly how much more blood the brain took to 

 perform the operation. Hence the plethysmograph is capable of mea- 

 suring the relative amount of mental power required by different per- 

 sons to work out the same mental problem. Indeed, Mr. Gaskell 

 suggests the use of this instrument in the examination-room, to find 

 out, in addition to the amount of knowledge a man possesses, how 

 much effort it causes him to produce any particular result of brain- 

 work. Dr. Mosso relates that, while the apparatus was set up in his 

 room in Turin, a classical man came in to see him. He looked very 

 contemptuously upon it and asked of what use it could be, saying that 

 it couldn't do anybody any good. Dr. Mosso replied, " Well, now, I 

 can tell you by that whether you can read Greek as easily as you can 

 Latin." As the classicist would not believe it, his own arm was put 

 into the apparatus and he was given a Latin book to read. A very 

 slight sinking of the curve was the result. The Latin book was then 

 taken away and a Greek book was given him. This produced, imme- 

 diately, a much deeper curve. He had asserted before that it was 

 quite as easy for him to read Greek as Latin, and that there was no 

 difficulty in doing either. Dr. Mosso, however, was able to show him 

 that he was laboring under a delusion. Again, this apparatus is so 

 sensitive as to be useful for ascertaining how much a person is dream- 

 ing. When Dr. Pagliani went to sleep in the apparatus, the effect 

 upon the resulting curve was very marked indeed. He said afterward 

 that he had been in a sound sleep, and remembered nothing of what 

 passed in the room that he had been absolutely unconscious ; and 

 yet, every little movement in the room, such as the slamming of a door, 

 the barking of a dog, and even the knocking down of a bit of glass, 

 were all marked on the curves. Sometimes he moved his lips and gave 

 other evidences that he was dreaming ; they were all recorded on the 

 curve, the amount of blood required for dreaming diminishing that in 



