48 David H. Dolley, 



al capacity would not only be expected but it can be traced cyto- 

 logically, step by step. From the beginning of activity, as the case 

 for the waste products needs no argument, there are two independent 

 processes combining to handicap the cell in its further progress, 

 namely, the reactive effect on the cell itself of its own waste pro- 

 ducts and its progressive loss of substance. 



It is not only that so great are the reserve powers of the cell, 

 as will be elaborated, that in ordinary experimentation of excita- 

 tory stimulation, whether of nerve or muscle, the factor of consump- 

 tion of substance is within considerable limits of time and degree of 

 little moment and hence is missed. The point is that it must be 

 missed for it is identical as regards functional display with the other 

 factor of waste products. The proof of this is apparent from the 

 anatomical interpretation. As the logical deduction from his fin- 

 dings (1913 b) in confirmation of R. Hertwig's (1902) theory of the 

 origin of chromatin, this substance is held by the writer to represent 

 the essential, though not necessarily the sole source of energy. To 

 its elaboration, as the chief type of final product, both nucleus and 

 plasma integrate as the single response to any form of excitation. 

 Waste products do no more than progressively inhibit its formation. 

 Activity finally comes to use it up faster than it is formed. In either 

 case, though from diametrically opposite causes, it will be seen that 

 the substance that supplies energy ceases to be available. Function 

 is impeded or stops in both. In both cases, the phenomena of function 

 disturbed by fatigue depend upon the state of the same substance 

 and this substance tends toward the same state. This is why 

 irritability is lowered in both with the progress of activity, for ir- 

 ritability for the nerve cell depends upon the presence of its chro- 

 matin. The only condition that may qualify this would appear to 

 be that the chromatin formed during depression may be modified or 

 deteriorated. 



The only difference between the effect of the factors as regards 

 function is that total depression proper may intervene at any stage, 

 while total exhaustion of excitation occurs only at a fixed limit, 

 coming as a summation of endeavor. However handicapped, if it can 



