234 THE POPULAR SCIENCE MONTHLY. 



impulse itself must be sufficient in intensity ; the "points" (in railway 

 phraseology) must be "open," the line must be clear, and the circula- 

 tion must be so balanced that it is ready to surge in the required direc- 

 tion. The outcome may be defective by the failure of any of these 

 conditions, and an improved adjustment in some needed respect may 

 at once enable a correct result to be got. Thus, a familiar name or 

 word may escape the memory, and for a time every effort may fail to 

 recall it. Then, for example, a more successful focusing of the circu- 

 lation taking place in the ideational center, the word comes up without 

 apparent effort. From this point of view, " unconscious cerebration " 

 means simply "better adjustment." 



If the radiation be toward a motor center, we find in the latter all 

 the conditions favorable for liberating its energy. In the waking state, 

 in the absence of fatigue or disease, the center requires little more than 

 permission to do its work. All the potential conditions for discharge 

 are already there. With the stimulus communicated from another 

 center, we have simultaneously molecular agitation and vascular ex- 

 citement. The latter acts in two ways. In the first place, by deriva- 

 tion, it removes the inhibitory action of other parts of the brain ; and 

 in the second place, it further directly stimulates the molecular move- 

 ment. The immediate result is turgescence or orgasm in the center 

 itself. Then, the general law in physics, that action and reaction are 

 equal and contrary, must here hold good. If the surroundings, there- 

 fore, be stable, natural relief will be got by the overflow or discharge 

 of energy into a motor nerve, and contraction of a muscle will be the 

 result. On the other hand, if the support afforded to the center be 

 insufficient, the vascular turgescence will to some extent spend itself 

 in displacing the surrounding tissues, and the intended movement will 

 either not take place, or it will fail in precision and strength. 



My object in the present paper has been rather to give prominence 

 to what I consider a neglected factor in cerebral physiology than to 

 attempt its application to all possible instances. I shall be satisfied if 

 I have said enough to show the importance of investigation in the 

 direction I have indicated. Indeed, w r hen one reflects on how much 

 research is devoted to the minute structure of the brain itself, it seems 

 surprising that so little attention is given to what may be called intra- 

 cranial physics. We have here a field which is at least as likely to be 

 fruitful in results as the attempt to measure and classify all the varie- 

 ties of nerve-cell, or to unravel the complex network of nerve-fibers. 



Within the skull we have an imperium in imperio, where, with 

 loyal fealty to the interests and claims of imperial unity, the rights of 

 " home-rule " are jealously conserved. As the speck of protoplasm 

 requires the restraint of the cell-wall to enable it to develop and exer- 

 cise some specific form of energy, so the brain-mass has its form 

 molded, and its development directed, and, especially, its energies 

 exercised under the severe repression of membrane and bone. Then, 



