SCIENCE. 



H5 



The higher functions of the nerve-cell, those connected 

 with mental processes, is a field too vast to be entered at 

 this time. The double telegraph line of nerve, motor and 

 sensor in their effect, but, as Vulpian has proved, precisely 

 alike in function, are the avenues of ingress and egress. 

 Every sensory impression is received by the thalatui optici ; 

 every motor stimulus is sent out from the corpora striata. 

 In the acts denominated reflex, the action goes from the 

 spinal cord and is automatic and unconscious. Should the 

 impression ascend higher to the sensory ganglia, the action 

 is now conscious though none the less automatic. Finally, 

 should deliberation be required before acting, the message 

 is sent to the hemispheres by the sensory ganglia and will 

 operates to produce the act. Based on principles which 

 can be established by investigation, a true psychology is 

 coming into being, developed by Bain Maudsley, Spencer 

 and others. A physiological classification of mental oper- 

 ations is being formed which uses the terms of metaphysical 

 psychology, but in a more clearly defined sense. Emotion, 

 in this new science, is the sensibdityof the vesicular neurin 

 to ideas. Memory, the registration of stimuli by nutrition. 

 Reflection is the reflex action of the cells in their relation 

 to the cerebral ganglia. Attention is the arrest of the trans- 

 formation of energy for a moment. Ratiocination is the 

 balancing of one energy against another. Will is the 

 reaction of impressions outward. And so through the 

 list. 



Among the physical aspects of the mind-question, 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 dis- 

 puted by no one in these days. Hence, the brain must act 

 like a machine and transform energy. There is then a 

 purely physiological representation of mental action, con- 

 cerned with forces which are known and measurable. The 

 researches of Lombard long ago showed the concomitant 

 heat of mental action. Recent researches are equally in- 

 teresting, which show that mental operations are not in- 

 stantaneous 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. The mechanism of 

 such a process is the following : Suppose the sound 

 " A " is heard by the ear. After a latent period it is trans- 

 lated to some nerve cells and hence to the brain. From 

 the brain it goes to other cells, ganglion cells, and to other 

 nerves, and then to the different muscles of the chest and 

 larnx, and then follows the audible response "A." Now 

 since this whole process requires only one-sixth of a second, 

 the question arises, how much of it is psychical. To an- 

 swer it, the experiment is repeated but with this difference, 

 that the particular sound to be used is unknown to 

 the experimenter. Before the sound can be repeated by 

 him therefore, a distinct act of discrimination is required, 

 and the time taken is longer. Calling the time in the 

 first experiment a, and in the second b, the difference b — 

 a is the time required for two distinct actions : one, that 

 of distinguishing the sound, and the other, that of will- 

 ing the corresponding movement. If now it be agreed 

 that only the sound "A" shall be responded to when 

 called, these may be separated since no other sound being 

 responded to the latter action is eliminated. If the time 

 now required be called c, the difference c — a represents the 

 time required for forming a judgment, and c — b the time 

 required for a volition. In making these measurements, 

 Donders used an instrument devised by him, called a 

 noemotachograph and also a modification of it called a 

 noemotachometer. By these instruments different points 

 of the body can be irritated, different sounds can be pro- 

 duced, and different color or letters can be shown, all by 

 the electric spark. By subtracting the simple physiological 

 time from the time given in any experiment, the time neces- 

 sary for recognition may be obtained. By an addition to 

 th« apparatus, a second stimulus may be made to follow the 

 first, either on the same or on a different sense ; thus enab- 

 ling the time necessary for a simple thought to be deter- 

 mined. As a result of his experiments, Donders found 

 that the value b — a in the case of a simple dilemma was 



seventy-five thousandths of a second, this being the time 

 required for recognition and subsequent volition. In the 

 same way c — a has been shown to be forty-thousandths 

 of a second, being the time required for simple 

 recognition ; there is left thirty-five thousandths of a 

 second as the time required for volition. Moreover, by 

 independent measurement with the noemotachometer, ex- 

 actly the same time, one twenty-fifth of a second, is found 

 necessary to enable a judgment to be formed about the 

 priority of two impulses acting on the same sense. If they 

 act on different senses, more time is necessary. So also 

 more time is required to recognize a letter by seeing its form 

 than by hearing its sound. A man of middle age then, 

 thinking not so very quickly, requires one twenty-fifth of a 

 second for a simple thought. 



Anothei important fact concerning nervous action is that 

 its amount may be measured by the quantity of blood con- 

 sumed in its performance. Dr. Mosso of Turin has de- 

 vised an apparatus 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 experi- 

 mented on, is placed in a cylinder of water and tightly en- 

 closed. 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 fur- 

 ther 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 di>tinctly how much more 

 blood the brain took to perform the operation. Hence the 

 plethysmograph is capable of measuring the relative amount 

 of mental power required by different persons 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 posses- 

 ses, 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 immediately, 

 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 dreaming. When Dr. 

 Pagliani went to sleep in the apparatus, the effect upon the 

 resulting curve was very marked indeed. He said after- 

 ward that he had been in a sound sleep and remembered 

 nothing of what passed in the room — that he had been ab- 

 solutely 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 emo- 

 tions 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. 



In an address of the retiring President of this Associa- 

 tion, delivered but a few years ago, I find this sentence : 

 " Thought cannot be a physical force, because thought ad- 

 mits of no measure." In the light of the rapid advances 

 1 lately made in investigating mental action, we see that in 



