( 701 ) 
of dissimilation. As in the circumstances, under which we consider 
the physiological systems, a slight exchange of matter is always 
taking place, a part of the first system passes continually into the 
second. In this case we have therefore to deal with a stationary 
state founded on a chemical equilibrium. The third condition of 
equilibrium is, therefore, not exactly satisfied, and it is only by 
approximation, that we deal with these systems as if they were in 
a. state of equilibrium. 
In the first place I shall discuss the results which may be derived 
from the principle of equilibrium for the reflex-apparatus; and in 
the second place the law according to which the passage of the 
products of assimilation to the products of dissimilation takes place. 
When discussing states of equilibrium we have in the first place 
to know, what the nature and the causes of the equilibrium are. 
As to the nature of the equilibrium in physiological systems, we 
must consider it as stable, because all physiological experiments have 
proved, that a stimulus ofa finite value is required to bring about a finite 
effect. No infinitely small cause, therefore, is capable of bringing 
about a finite change of state in these systems '), 
As cause of the equilibrium we must regard in the first place 
the active tendencies of the system. If this were the only cause 
of the equilibrium, external influences or changes in the initial state 
of the system, infinitesimal in amount, should be sufficient to produce 
changes in this system *). The method of the just perceptible differ- 
ences which is also physiologically applicable, shows clearly that 
this is not the case. Beside active tendencies also passive resistances 
which prevent changes must exist in physiological systems. 
When the reflex-apparatus is subjected to the action of a stimulus 
of short duration, it undergoes a series of changes, through which 
it finally returns to its initial state. We may therefore say that a 
eyclical process takes place. As far as I know, there are no 
measurements about the duration of this cyclical metabolic process 
for a simple reflex-apparatus. For the intact organism we may learn 
it approximately from ergographical curves. If the cyclical metabolic 
process shall be complete, then for not too short a period every suc- 
cessive elevation must be equal to the preceding and must not differ 
considerably from the very first elevation. It appears from the 
ergograms communicated by LEHMANN ®), that this is the case for a 
1) Grass, |. c. p. 112. 
2) Gisss, |. c. p. 111. 
8) Leumann, Körperlichen Ausserungen psychischer Zustände. 1901, plate X and XIX, 
