JUNE 21, 1912] 
latter. This ean again be proved by measur- 
ing the influence of the change of concentra~ 
tion of a salt solution on that outer surface, 
which is exactly the same as it was before the 
pressure was applied. If, however, we connect 
this part of the skin and an intact part of 
the skin with a pair of calomel electrodes 
filled with a KCl solution of the same concen- 
tration, we get an E.M.F. of the same order 
of magnitude and the same sign, as if the 
skin at the pressed spot had been removed. 
This experiment, which is very striking, 
indicates also that the current of injury is due 
to the existence of a potential difference at 
the inner surface of the skin of the apple 
which depends upon the integrity of a definite 
structure. 
3. An attempt to account for the nature of 
this E.M.F. led to the discovery that salts and 
acid, if applied in the same concentration to 
the outside surface of an apple, give rise to 
differences of potential of the same order of 
magnitude as found in the current of injury. 
The E.M.F. of the cell 
n/10 NaCl | uninjured apple | 2/1,000 NaCl | 
n/10 NaCl (1.) 
is greater than that of the following cell 
n/10 NaCl | uninjured apple | /1,000 HCl | 
n/10 NaCl (II.) 
In (1.) the E.M.F. was .088 volt, in (II.) .038 
volt. 
4. Since this difference is of the order of 
magnitude of that found in the current of in- 
jury; it was natural to test the action of the 
juice pressed out of the apple. Its conductiv- 
ity was found to be K,o—.00226. This 
would correspond to a concentration of n/58 
if the electrolyte contained in the sap were 
KCl, or n/170 if it were HCl. The apple 
juice contains a considerable amount of malic 
acid. Nevertheless it does not have the nega- 
tive effect characteristic of the acid. If the 
negative potential on the inside of the skin is 
due to a layer of acid it must differ in its ac- 
tion from the sap pressed out from the apple. 
These experiments indicate that the current 
of injury of the apple is due to a potential 
difference at the inner limit of the skin or 
SCIENCE 
971 
membrane; and that this potential difference 
depends upon the integrity of a preformed 
structure. This structure may give rise to 
the formation of a film of an acid but this is 
hypothetical. 
Our observations prove that MHermann’s 
alteration theory of the current of injury can 
not be correct. This theory assumes that the 
difference of potential exists at the injured 
surface, while the experiments mentioned 
here show that the seat of the potential dif- 
ference is, at least for the apple, not at the 
seat of the lesion, but at the inner limit of the 
intact skin or membrane and its intact adja- 
cent layer. DuBois’s preformation theory is 
confirmed, although in a different form from 
that which this author suggested. 
Jacques Logs, 
REINHARD BEUTNER 
DEPARTMENT OF EXPERIMENTAL BIOLOGY, 
ROCKEFELLER INSTITUTE 
SOCIETIES AND ACADEMIES 
THE BIOLOGICAL SOCIETY OF WASHINGTON 
THE 498th regular meeting of the society was 
held in the assembly hall of the Cosmos Club on 
April 13, 1912, with President Nelson in the chair. 
Under the head of General Notes, Dr. B. W. 
Evermann exhibited dyed and undyed skins of fur 
seals from the Pribilof Islands, and made remarks 
on the commercial classification of skins and on 
the aims of the Bureau of Fisheries regarding the 
fur-seal industry. 
The paper of the evening was by Mr. Chas. 
Sheldon on ‘‘ Winter Animal Life about the Base 
of Mt. McKinley.’’? Mr. Sheldon gave an inter- 
esting account of his experiences with the birds 
and mammals of the Mt. McKinley region during 
the winter of 1907-08, describing in detail the 
food and habits of the Alaska jays, the mallard 
ducks, which were found wintering where local 
conditions favored open water and sufficient food, 
the lynx, conies, foxes, caribou, moose and sheep. 
Mr. Sheldon’s lecture was admirably illustrated 
with numerous lantern slides, showing his cabin, 
general and detailed views of the country and 
long- and short-range snap shots of all the larger 
animals of the region. 
THE 499th regular meeting of the society was 
held in the assembly hall of the Cosmos Club on 
