778 Dynamic Theory. 



of other centers by external stimuli divert to them the blood supply, 

 and second, by furnishing other outlets for the internal stimuli than 

 those of the emotions, the excitement of those centers is reduced. One 

 great emotion will neutralize a smaller one. Enemies be- 

 come friends when both are threatened by a common peril. 

 Wild beasts cease to fear men when confronted by some ter- 

 rible natural calamity. 



Starvation is a mortal enemy of emotions. Deprived of 

 proper physical nourishment from the blood, all the brain 

 centers rapidly lose their force and activity. The sensations 

 expressed by pity, love, hate, anger, revenge, and all the 

 rest, disappear in the presence of hunger, and nothing so 

 quickly subdues a ravenous beast. 



FIG. 378. Diagrams showing interruptions by sensory stimuli of auto- 

 matic movements of infants. 



a, a, s, d- Periods in which the automatic movements were performed. 



b, 6. Periods of musical sound during which attention was diverted to 

 the sound and the movements stopped. 



c, e. Periods in which light was exhibited- 

 d. Light withdrawn. 



In experimenting with infants, it has been observed that 

 their automatic or spontaneous movements have been ar- 

 rested by a stimulation of sight or sound and temporarily 

 suspended. The diagram, from Warner, shows this experi- 

 ment graphically. Several authors call this action of the 

 sound or light " inhibitory. " During the continuance of 

 the stimulation b/ the light or sound, the attention of the 

 child was fixed, that is, the circulation of the blood and the 

 accumulated nervous energy which before went to the mus- 

 cles, was now directed by the stimulus to the brain and went 

 to the differentiation of brain tissues. Such inhibition is not 

 a negative process, but simply divertive and directive, and 

 the term is not a good one for the case. If the cerebral hem- 

 ispheres be taken out of a live frog, leaving the optic thalami, 

 optic lobes, medulla oblongata and spinal cord uninjured, 

 reflex action can be got by irritating a limb, say a toe, by dipping it 

 into very dilute sulphuric acid. After a moment, the length of which 

 must be noted, the limb will be withdrawn. If the experiment be tried 

 of putting the toe in the acid, and at the same time stimulating the 

 optic thalami, or optic lobes, by touching with a crystal of rock salt, it 

 will be found that the reflex withdrawal of the toe will require a much 

 greater length of time. This, too, is inaptly explained as resulting 

 from the "inhibitory " action of the optic thalami, or optic lobes. The 

 fact is, I take it, that when these lobes are irritated a part of the energy 



