606 THE POPULAR SCIENCE MONTHLY, 



. . . She kneels, falls face forward to the ground, where she remains for hours 

 in the attitude of crucifixion. Other attitudes are taken during the ecstatic con- 

 dition, which comes to an end in the midst of alarming symptoms of impending 

 death." 



I will, in conclusion, venture upon a few suggestions as to the ex- 

 planation of the phenomena of hypnotism and its allied states. 



Our cerebral life depends upon the associated activity of innumer- 

 able nerve-cells grouped into clusters or centers, each center being 

 more directly related with some sensory or some motor function. 

 Thus there are visual centers, auditory centers, tactile centers, which 

 form the terminal stations of the nerve-fibers leading from the organs 

 of sight, hearing, and touch. There are also so-called motor centers, 

 the nervous discharges from which, traveling down to the spinal cord, 

 determine movements of the head, trunk, and limbs. 



A network of the finest nerve-fibrils of astounding complexity 

 brings the individual cells of each center into relationship with one 

 another, and with the cells of the other centers. This physical asso- 

 ciation of our brain-elements is the material substratum of the psychi- 

 cal process of association of ideas which forms the groundwork of our 

 intellectual life. All the higher manifestations of mind are correla- 

 tives of the harmonious co-operation of numerous brain-elements. 

 Even what appear to be simple states of consciousness are often the 

 result of association. Hence any disturbance in the mutual equi- 

 librium of the cerebral centers speedily leads to alterations of those 

 resultants of forces of which perception, thought, will, emotion, are 

 the subjective manifestations. 



One of the most striking properties of the nervous system is that 

 by which the activity of one portion may be arrested or prevented 

 " inhibited " by the activity of another. To give a familiar instance, 

 the action of the respiratory centers is suddenly inhibited by certain 

 excitations of the sensory nerves, as we have all experienced on re- 

 ceiving the first splash of a cold shower-bath. In the cerebral sphere, 

 inhibition of one tract by another is the mechanism which lies at the 

 root of the higher exercise of our faculties. "When we choose, for 

 instance, or exercise will-power, the corresponding state of our nervous 

 organism is one involving more or less complex inhibitions. The sense 

 of moral effort is the subjective equivalent of powerful inhibitions 

 of brain-tracts in a state of high tension. The power of mental 

 concentration rests likewise upon similar inhibitions. When we at- 

 tend closely to a sensory impression, or to a train of thought, the ex- 

 citability of every part of the brain except that actually engaged in 

 the act is diminished by an inhibitory action of the working portion. 

 Thus, when wo say that anger or fear paralyzes, we allude in very 

 accurate language to the inhibitory influence which powerful emotion 

 exercises upon the other cerebral functions. 



I have said that physiological sleep can be induced by certain 



