No. 2.] CHANGES IN NERVE CELLS. 141 



ing, active cell. The cell is perhaps as actively at work in 

 phases of anabolic as in katabolic changes. Neither is it anoma- 

 lous that these changes do not go on in the cell continuously 

 and with equal steps. Perhaps no instance of living cells work- 

 ing thus continuously could be cited in all biology. Everything 

 seems to be done in rhythm. And if the cells of a cleaving 

 ovum pass through "resting stages " and " stages of activity " ^ 

 (83, p. 292), and if the bodies of school children, as Bowditch ^ 

 has shown, grow not continuously and equally, but now fast 

 and again more slowly, there is every reason to suppose that 

 nerve cells may follow the same rule. Thought, psychologists 

 tell us, flows not continuously, but in waves. And general 

 experience proves that the beat of the waves of thought is not 

 equable and uniform, but variable in the extreme. Now they 

 dash high, now they run in a gentle ripple, now there is the 

 calm of stupidity or sleep. And may not thought be an index 

 to the activity of nerve cells } 



I have already stated that these curves are provisional. In 

 fact, they have been introduced with the purpose of showing 

 that they cannot be wholly relied upon, rather than of attaching 

 permanent value to them. This is because an important factor 

 in their shaping has been entirely ignored. This factor is, of 

 course, the normal tendency toward activity or toward rest, 

 toward anabolism or toward katabolism present in the cells 

 while the stimulus is being applied. 



From the first, we have been endeavoring to discover only 

 such changes as occur in the normal functional activity of the 

 nerve cell. That changes already described do relate to normal 

 and not to pathological processes seems conclusively proved. 

 If, then, these changes are normal, there should be no difficulty 

 in demonstrating a similar rhythmic curve of rest and work in 

 the normal daily activity of the animal. No more fundamental 

 rhythm exists, either in physiology or psychology, than that of 

 activity alternating with rest, sleep with waking. And this 

 rhythm, from such work as Lombard (45, pp. 1 1 ff.) has done, 



1 Ref. W. K. Brooks' " Alternations of Periods of Rest with Periods of Activity 

 in the Segmenting Eggs of Vertebrates," Studies Biol. Laborat., Johns Hopkins 

 University, Vol. II., 1882. 



2 H. P. Bowditch, "The Growth of Children," Mass. State Board of Health, 

 Twenty-second Annual Report, p. 509. Boston, 1891. 



