390 THE CANADIAN NATURALIST. [Vol. ix. 



distinctly how much more blood the braia took to perform the 

 operation. Hence the plethysmograph is capable of measuring 

 the relative amount of mental power required by different per- 

 sons to work out the same mental problem. Indeed Mr. Glaskell 

 suggests the use of this iostrument 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 could'nt 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 im- 

 mediately, 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 labouring under a delusion. Again, 

 this apparatus is so sensitive as to be useful for ascertaining how 

 much a person is dreaming. 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 

 souud 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 the extremities. The emotions 

 too left a record. When only a student came into the room, 

 little or no effect appeared in the curve. But when Professor 

 Ludwig himself came in, the arteries in the arm of the person 

 in the apparatus contracted quite as strongly as upon a very 

 decided electrical stimulation." 



Professor Barker is a strong believer in the capacities of the 

 chemist and the great things yet to be accomplished by him 

 With reference to protoplasm he says : 



