NovEMBER 22, 1918] 
than uninjured regions, as determined by our 
methods; and further that this increase in 
metabolic rate is the result of the stimulation 
of cutting, since it does not occur if the cut- 
ting is done under anesthesia. We have also 
shown that this alteration of metabolic rate 
as the consequence of injury occurs not only 
at the cut surface but involves adjacent un- 
injured regions also, in proportion to their 
distance from the cut. Tashiro! has further 
found that injury invariably increases the 
carbon dioxide output of living material, and 
he believes this reaction to injury to be an 
infallible sign that the material is living. 
In the text-books of physiology, explanations 
of the current of injury are usually based upon 
supposed alterations of membranes, concentra- 
tions of electrolytes, etc., at the cut surfaces,— 
that is, the cut place is supposed to cause the 
phenomenon. But our observations show that 
the change in metabolic rate occurs not only 
at the cut surface but for some distance away 
from it; and an experiment of Bose’* demon- 
strates that the region of électronegativity 
also exists not merely at the site of injury 
but for a considerable distance away, diminish- 
ing in fact with distance. Here again the 
current runs parallel with the metabolic con- 
ditions at and near the injured regions. Bose 
concluded that the actual injury to the cells 
is not directly the cause of the electronega- 
tivity but that the stimulation due to the 
injury produces the electric change; and this 
stimulation, like many others, is transmitted 
with a decrement to surrounding regions. In- 
jury is thus a form of stimulation and our ex- 
periments and those of Tashiro show that the 
stimulation of injury produces in the organ- 
ism an increase in metabolic rate. Hence, as 
in the preceding case, we may suggest that the 
current of injury arises through the fact that 
the site of injury and adjacent regions are 
regions of increased metabolic rate and thus 
13 A chemical sign of life. 
14‘‘Comparative Electro-physiology,’’ 1907, pp. 
154 ff. Bose has a great deal of interesting ex- 
perimentation on the bioelectrie currents but un- 
fortunately it is often very difficult to grasp his 
exact meaning. 
SCIENCE 
521 
are electronegative to intact regions, where the 
rate is lower. 
3. The Current of Action—Whenever any 
living material is “stimulated,” the stimu- 
lated region becomes ipso facto a region of 
electronegativity with respect to non-stimu- 
lated areas. In order to analyze this univer- 
sal phenomenon, it is necessary to know what 
the nature of stimulation is. Physiologists 
are still very far from a solution of this diffi- 
cult and fundamental problem. I venture to 
suggest, however, that everything that we 
know about stimulation indicates that increase 
in metabolic rate is its principal characteristic. 
Thus the oxygen consumption increases, the 
carbon dioxide output increases, the produc- 
tion of synthesized materials and of waste 
products is accelerated, the energy produced is 
augmented.1® Tashiro,1®¢ for instance, after 
testing various kinds of plant and animal 
tissues, says: “In all cases stimulation causes 
an increase in carbon dioxide. We could 
never find any response unaccompanied by an 
outburst in carbon dioxide.” 
Every cell carries on a specific kind of 
metabolism, resulting in specific end products. 
As far as we know, each cell is always pro- 
ducing these whether it is in a stimulated con- 
dition or not, and the rate at which it does 
this is a measure of the degree to which it is 
alive. Thus Tashiro finds that all living sub- 
stances give off carbon dioxide, and the rate 
of this output runs parallel to other manifesta- 
tions of life, as relative irritability, rapidity of 
response, rate of conduction, ete. Let us con- 
sider very briefly the three chief active tissues 
of the body,—gland, muscle and nerve. In 
any particular kind of gland cell, barring spe- 
cial experimental or pathological conditions, 
there are in general the same kinds of gran- 
ules to be found at all times. As far as one 
can determine, the rate of formation and dis- 
charge of granules alone is variable—not their 
content. The essential effect of stimulating 
the gland cell through its nerve is an increase 
15 These statements can be verified in any of 
the recent text-books of physiology as Bayliss, 
Howell, Stewart, ete. 
16 Loc. cit., p. 99. 
