SCIENCE. 
1 15 
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 thalami 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 sensibility of 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. 
Another 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 distinctly 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 
lately made in investigating mental action, we see that in 
