1897.] Psychology. 733 
gators have studied the problem in one or other of these forms, among 
them may be noted Féré, Patrick and Gilbert, Frey, Bolton, Bergström 
and Henri. 
In an article in the Année psychologique for 1896, M. Henri gives a 
résumé of the various investigations and the methods used in each. He 
emphasizes the importance of distinguishing the different factors in- 
volved in both mental and physical work, and of studying each one 
separately by appropriate experimental methods. Among these fac- 
tors he specifies in particular attention, voluntary effort, the psychic 
processes of memory, and imagination. Little progress has as yet been 
made in the way of investigating effort except in the study of patho- 
logical cases such as aboulia. As for attention, while considerable 
work has been done in this field, the investigations have generally had 
for end to determine the mental effects of fatigue and other variations 
in the conditions, rather than to measure the physical effects of varia- 
tions in the attention. Memory has been, perhaps, more systematically 
studied than any of the other factors. 
The investigation of the effect of intellectual work on the pulse and 
other functions which MM. Binet and Courtier have undertaken 
seems most likely, of all methods so far devised, to furnish a measure 
of psychical work in physical terms. A series of papers on the subject 
by these authors has appeared in the Année psychologique, the first in 
the issue for 1895, and four others in the last volume.? In approach- 
ing the question it was first of all necessary to study the effect of 
changes in respiration on the heart beat and blood supply. A large 
part of the first paper is accordingly taken up with this and with an 
examination of possible errors in the apparatus. The instrument used 
was the plethysmograph of Hallion and Conte. This consists of a 
rubber cylinder, which is grasped firmly by the hand. The outer sur- 
face of the hand is covered with a tight-fitting glove, so that any ex- 
pansion in volume of the hand (due to increased blood pressure) takes 
effect on the inner surface, and results in diminishing the volume of 
the rubber cylinder; the latter communicates by means of a tube with 
a flexible drum. When the cylinder is compressed by the hand the 
drum rises, and the effect is recorded by means of a pen attached to 
the drum. The apparatus was found to be very serviceable, and was 
remarkably free fromerror. In addition to the frequency and strength 
of the pulse beat, the dicrotism, or break in the beat, was clearly 
marked in the diagrams, and proved an important factor in the 
results. 
? Vol. III, 1896, published this spring. 
