1913.] BRAIN CELLS AND BRAIN FUNCTIONS. 399 



gical shock, produce similar outward manifestations and identical 

 brain cell changes. 



It is, therefore, the purpose of this paper to present the definite 

 results of certain laboratory researches which show certain relations 

 between the alteration in brain functions and alterations in the brain 

 cells. 



Fear. — Our experiments showed that the brain cell changes due 

 to fear may be divided into two stages : First, that of hyperchro- 

 matism — stimulation ; second, that of hypochromatism — exhaustion. 

 Hyperchromatism was shown only in the presence of the activating 

 stimuli or within a very short time after they had been received. 

 This state gradually changed until the period of maximum exhaus- 

 tion was reached, about six hours later. Then a process of recon- 

 struction began and continued until the normal state was again 

 reached. 



Fatigue. — Fatigue from overexertion produced in the brain cells 

 like changes to those produced by fear, these changes being propor- 

 tional to the amount of exertion. In the extreme stage of exhaus- 

 tion from this cause we found that the total quantity of Nissl sub- 

 stance was enormously reduced. If the exertion is too greatly 

 prolonged, it may take weeks or months for the cells to be restored 

 to their normal condition. In fact, in exhaustion from the emotions 

 or from physical work a certain number of brain cells are perma- 

 nently lost. This probably explains the fact that an athlete or a 

 race horse trained to the point of highest efficiency can but once in 

 his life reach his maximum record. Under certain conditions, how- 

 ever, it may be possible that though some chromatin is forever lost, 

 the remainder may be so remarkably developed that for a time at 

 least it will compensate for that which is gone. 



Hemorrhage. — The loss of blood from any cause, if sufficient 

 to reduce the blood pressure, will occasion a change in the brain 

 cells, provided the period of hypotension lasts more than five min- 

 utes. This time limit is a safeguard against permanent injury from 

 the temporary hypotension which causes one to faint. If the hem- 

 orrhage is long continued and the blood pressure is low, there will 

 be a permanent loss of some of the brain cells. This is why an indi- 



PROC. AMER. PHIL. SOC, LU. 2IO H, PRINTED JULY l8, I9I3. 



