NovEMBER 22, 1918] 
as our conception demands, it is characterized 
by an exceedingly high rate of metabolism. 
This is demonstrated not only by its blood 
supply, its great susceptibility to lack of oxy- 
gen, to anesthesia, to cyanide and other pois- 
ons, but also by direct measurements of its 
rate of oxygen consumption. Thus, Alex- 
ander and Cserna’ find that the oxygen con- 
sumption of the brain is vastly greater than 
that of equal weights of any other organs, and 
MacArthur and Jones?° that the cerebrum and 
cerebellum respire faster than any other parts 
of the central nervous system, the rate de- 
creasing gradually from these parts posteriorly. 
The nervous system by virtue of its intrin- 
sically high metabolic rate.is able to control 
other parts of the body, and to increase their 
metabolic rates by sending impulses along 
the nerves. 
It should be mentioned that stimulation is 
characterized not only by the acceleration of 
the metabolic processes but also by other 
changes, which may well be the consequences 
of this acceleration, such as alteration of the 
colloidal state (probably in the direction of 
liquefaction), increase in permeability, and 
other effects. 
4. Galvanotaris—The metabolic gradient 
also furnishes us with a logical explanation 
of the phenomena of galvanotaxis. It is well 
known that many animals when placed in an 
electric current will turn their anterior ends 
toward the cathode and travel to the cathode, 
maintaining such an orientation. Now as I 
pointed out in the first section of this paper, 
the anterior ends of a variety of organisms 
have been shown to have a higher metabolic 
~ rate than other parts of the body and to be 
electropositive (internally) to other parts. 
Since then the anterior end is positively 
charged or at least possesses the properties of 
an anode, it must when placed in the current 
be directed toward the cathode and it will tend 
to travel towards the cathode like any other 
positively charged material. Animals on the 
same basis might also travel backwards to the 
anode. Galvanotaxis is then a real taxis, or 
19 Biochem. Zeitsch., LIII., p. 106. 
20 Jr, of Biol. Chem., XXXIL., p. 259. 
SCIENCE 
523 
forced orientation, in the sense of Loeb. A 
crucial test of this hypothesis can be made 
upon the oligochaete worms, where, as we 
know from experiment, there are two regions 
of high metabolic rate and of electropositivity, 
—namely, the anterior and posterior ends. 
These animals should then when placed in a 
current bend themselves into a U-shape, head 
and posterior end directed towards the cathode, 
and middle towards the anode, and travel to 
the anode maintaining such a posture. This 
is exactly what they do as first pointed out by 
Moore and Kellogg?! and since confirmed by 
Mr. Bellamy. 
5. Other Electric Phenomena.—Since regions 
of high metabolic rate are electropositive (in- 
ternally) to regions of lower metabolic rate, 
it follows that if any region can be made 
electropositive by running a current through 
it, that region must then have its metabolic 
processes accelerated and must thereby be 
stimulated, must become more irritable. 
That this is true is a familiar fact in electro- 
physiology. A constant current stimulates at 
the cathode when the current is made—that 
is, the region around the cathode becomes 
positively charged (or possibly becomes an 
anode in some other way), and hence has a 
higher metabolic rate, and serves as the source 
of the response. Similarly on the break of 
the current, the area of stimulation is that 
surrounding the anode, it having been shown 
that on the break the anode is really tempor- 
arily a cathode. Electrotonus is the same 
phenomenon. After prolonged passage of the 
electric current through a tissue, a large re- 
gion around the cathode becomes excessively 
irritable because it is full of positively charged 
particles,22, and a large region around the 
21 Biol. Bull., XXX., p. 131. 
22T do not wish to be understood as stating posi- 
tively that the electrical sign of various parts of 
the organism is actually due to their containing 
free particles of that sign. This seems the most 
convenient way of putting the matter but the facts 
in themselves do not serve to determine whether 
the charge is on the inside or on the surface or 
indeed what condition is responsible for it. The 
facts of electrotonus would seem to favor the idea 
that the charged particles are inside. 
