352 H. M. JOHNSON 



'central' portion of the machine's operations. . . . Every impres- 

 sion which impinges on the incoming nerves produces some discharge 

 down the outgoing ones, whether we be aware of it or not 



There are probably no exceptions to the diffusion of every impression 

 through the nerve-centers. The effect of the wave through the centers, 

 may, however, often be to interfere with processes, and to diminish 

 tensions already existing there; and the outward consequences of such 

 inhibitions may be the arrest of discharges from the inhibited regions 

 and the checking of bodily activities already in process of occurrence. 

 When this happens it probably is like the draining or siphoning of 

 certain channels by currents flowing through others. When, in walk- 

 ing, we suddenly stand still because a sound, sight, smell or thought 

 catches our attention, something like this occurs. But there are cases 

 of arrest of peripheral activity which depend, not on central inhibition, 

 but on stimulation of centers which discharge outgoing currents of an 

 inhibitory sort 



In general, however, the stimulating effects of a sense-impression 

 predominate over the inhibiting effects, so that we may roughly say 

 ... . . that the wave of discharge produces an activity in all 

 parts of the body. 



James here cites reports of Haller, Mosso, Fere*, Tarchanoff 

 and others as indicating that visual, olfactory and auditory stimuli 

 of short duration produced changes in the circulation, respiration, 

 secretion of the sudorific glands, and strength of contraction of 

 voluntary muscles. 



Perhaps the reference most nearly relevant to our experiment 

 is to the work of Fere*. I quote again from James : 



Every sensorial stimulus not only sends a special discharge into 

 certain particular muscles dependent on the special nature of the stim- 

 ulus in question .... but it innervates the muscles generally. 

 M. Fe*re" has given very curious experimental proofs of this. The 

 strength of contraction of the subject's hand was measured by a self- 

 registering dynamometer. Ordinarily the maximum strength, under 

 simple experimental conditions, remains the same from day to day. 

 But if simultaneously with the contraction the subject received a sen- 

 sorial impression, the contraction was sometimes weakened, but more 

 often increased. This reinforcing effect has received the name dyna- 

 mogeny. The dynamogenic value of simple musical notes seems to be 



