124 
tity in a twelve-hour hydrolysate as in a forty- 
eight-hour hydrolysate, but there is no ques- 
tion but that a part of the tryptophane nitro- 
gen would be in this fraction. 
It is of interest to note that McHargue ob- 
tained no “insoluble humin” for the twelve- 
hour hydrolysate of casein to which no carbo- 
hydrate had been added, and that his “ histi- 
dine” fraction is in excess of. that reported 
by other analysts. This observation accords 
beautifully with the idea of Gortner and 
Holm® that an aldehyde or ketone must be 
present to cause insoluble humin formation 
from tryptophane and that when insufficient 
aldehyde is present and the hydrolysis is not 
sufficiently prolonged the tryptophane will be 
(in part) precipitated by phosphotungstic acid 
and augment the “histidine” fraction [ef. 
Gortner and Holm]. 
However, all of this discussion, pertinent as 
it may be, would be trivial were it not for the 
fact that other workers may be led to accept 
McHargue’s conclusions and thus cause a fur- 
ther waste of money and energy in pursuing 
an illusive will-o’-the-wisp. 
In the introduction to his paper McHargue 
seems to argue that Van Slyke’s method may 
be applied directly to feeding stuffs without 
necessarily securing inaccurate results. Even 
if we should grant that the presence of carbo- 
hydrates per se did not vitiate the results, and 
all available evidence is contrary to such a 
conclusion, there would still remain other 
forms of nitrogen than proteins in the feeding 
stuffs which must necessarily appear in the 
various fractions and be wrongly calculated 
as amino acids. For example, Steenbock’ re- 
ports the presence of stachydrin in alfalfa and 
this substance would be calculated as “his- 
tidine ” in a Van Slyke analysis. I have else- 
where? fully discussed this point and therefore 
have no hesitation in making the following 
statements: (1) Proteins can not be hy- 
drolyzed with 20 per cent. hydrochloric acid at 
atmospheric pressure in the presence of a con- 
siderable quanity of carbohydrates without ap- 
preciably altering certain of the nitrogen frac- 
7H. Steenbock, Sci. Proc. Soc. Biol. Chem., 
XXVILI., 1916; J. Biol. Chem., Vol. 29 (1917). 
SCIENCE 
[N. 8. Vou. XLVIII. No. 1231 
tions of a Van Slyke analysis, and (2) a Van 
Slyke analysis applied to feeding stuffs, con- 
taining as they do non-protein nitrogenous 
compounds, gives no valid index as to the 
presence or absence of any individual amino- 
acid. Ross AIKEN GORTNER 
DIvIsION OF AGRICULTURAL BIOCHEMISTRY, 
UNIVERSITY OF MINNESOTA 
THE ACADEMY OF SCIENCE OF ST. 
LOUIS 
AT a meeting held on May 20 Professor Francis 
HE. Nipher stated that he had been making observa- 
tions on local variations in the electrical potential 
of the earth, due to local thunderstorms. The 
large masses in the Cavendish apparatus are con- 
nected with a wire passing through a window in 
the second story of the physics building to the 
earth. The wire is in contact with wet grass in 
the yard below, and with metal rods which are 
pushed down into wet ground to a depth of about 
15 inches. The lightning rod which grounds a high 
metal tower on the building, which was formerly 
used for wireless telegraphy, has been broken near 
the earth, and a gap of about two inches has been 
made in the rod. This rod can at any time be put 
in metallic contact with the large masses, by means 
of a knife switch. On several occasions during 
storms, sudden changes in the attraction of the 
large masses upon the suspended masses within the 
metallic shield have occurred, which it seems im- 
possible to explain except as due to enormous 
changes in the potential of the large masses, due 
to local changes in the electrical potential of the 
earth. Previous results show that this would 
change the gravitational attraction between the 
masses. N. M. Grier, 
Recording Secretary 
SCIENCE 
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