734 The American Naturalist. [ August, 
MM. Binet and Courtier note the existence of important individual 
differences in the effects of mental work on the physical processes. In 
some subjects these are confined almost wholly to changes in the res- 
piration, in others to the action of the heart, while in others they are 
felt more especially in the vaso-motor system. In general, the effect on 
the respiration is to make it more rapid and at the same time more 
superficial. The effects on the pulse curve most frequently observed 
are: 1st, diminution of amplitude; 2d, diminution of amplitude with 
change of form; 3d, diminution of amplitude, change of form and 
lowering of the level of the curve. One or other of these effects appear 
in almost all the subjects tested. 
In their later papers the authors consider in turn the various causes 
of change in the pulse. They confirm the well-known diurnal changes 
by numerous observations with their own method, e. g., that the pulse 
becomes more frequent and the dicrotism generally more marked im- 
mediately after a meal. As regards physicial exercise, they lay spe- 
cial stress on the changes that occur in the dicrotism according as the 
exercise is local, general and moderate, or general and fatiguing. 
The study of the effects of mental work is, of course, the most im- 
portant from the psychological standpoint, and here the authors have 
sought to combine tests of the heart and respiration with those of the 
pulse. In addition to the more delicate tests, involving simple mental 
operations, two of the subjects undertook a piece of severe and pro- 
longed mental work ; they spent seven hours working steadily at this 
task, merely resting at the end of each ‘hour for a time sufficient to 
perform the necessary tests. Comparing the results with those of a 
similar period passed under similar conditions but without work, the 
pulse was found to be considerably retarded in the former case, as com- 
pared with the latter, the retardation taking place especially in the 
early part of the period. The authors sum up their results on mental 
work as follows: “1. An energetic, but short mental effort produces 
an excitation of function, vaso-constriction, acceleration of the heart 
and of the respiration, followed by a very slight retarding of these 
functions ; in some of the subjects a blunting of the dicrotism. 2. In- 
tellectual work lasting for several hours with comparative immobility 
of the body produces a retardation of the heart and a diminution of 
the peripheral capillary circulation.” 
As regards the relation between physical and mental work, the 
authors are cautious in drawing conclusions. They observe a certain 
parallelism, in that a single energetic effort produces an acceleration of ; 
the heart and lungs, while a long-continued and fatiguing effort fre- 2 a 
