48 
IOWA ACADEMY OF SCIENCES. 
of chemical action. Recent work has made it clear that 
ciliary movement, and the still more specialized contrac- 
tion of a muscle-cell, are derivable from the simple 
conditions just sketched. 
Electricity is an invariable accompaniment of vital 
processes, whether in the contraction of a muscle-cell, the 
secretion of a gland-cell, the changes of nervous matter, or 
the truly striking discharge of a specialized electric organ. 
Electrolytic dissociation is the basis for the development 
of animal electricity in all its fascinating guises, chemical 
reactions continually altering the relations of ions. 
Differences of potential are due to the fact that not all 
parts of a cell or group of cells are active at the same 
time. It has long been known that protoplasm acquires 
an acid reaction as the result of its activity. In terms of 
physical chemistry, this fact means that positive hydrogen 
ions are set free. Such ions migrate from the active into 
the passive protoplasm more rapidly than do the anions, 
hence the regions where vital processes are taking place 
remain negatively charged, as all our experimental work 
has long shown. 
Y. THE IRRITABILITY OF PROTOPLASM. 
From the standpoint of cell-chemistry, the irritability 
of living matter is nothing more than the modifications 
induced by external conditions in the course of the trans- 
formation of matter and energy in the cell. A modern 
high-explosive is just as truly irritable as is protoplasm, 
having the equilibrium of its matter and energy disturbed 
by the impact of kinetic energy from without. In the case 
of living matter, the external energies productive of such 
disturbances are called “stimuli,” a somewhat unfortunate 
term. Obviously, the effect of stimulation, — the introduc- 
tion of kinetic energy from without, — is to divert the course 
of chemical reaction in the cell, causing a corresponding 
change in the kinetic energy liberated, — movement, heat ? 
light, electricity. The change in the electrical condition 
necessarily influences the behavior of the colloidal particles 
