374 
mechanism that works well supplies its own 
drive, it must not work too well; there must 
be some stimulus of difficulty. But may it not 
be argued that when a person loses interest 
in his work because his task is too easy, his 
mechanism too good, the reason must be either 
that the consummatory reaction is not con- 
nected with one of the great biological drives, 
or that he is not the kind of person to whom 
unsolved problems, that is, mechanisms some 
of whose parts are still undetermined, are ipso 
facto very strong drives; one who turns al- 
ways from the familiar to the new task? If 
he is of this type we may as well say that he 
is urged by the drive of curiosity, whose bio- 
logical value is clear. In other words, while 
special talents, specially good mechanisms, 
may involve special readiness of their con- 
summatory reactions to be excited, without 
certain general traits of the personality like 
energy, curiosity, pugnacity, mere excellence 
of a mechanism would not suftice for its pro- 
longed and effective use. The reviewer has 
elsewhere pointed out the possible function 
of the activity attitude in connection with 
those intellectual tasks which are only in- 
directly related to the primitive drives. 
Of the many other points for discussion 
that are suggested by these lectures, there is 
space to mention but one. Those of us who 
hold, with the author, that introspection has 
furnished some scientific results “with such 
regularity that they command general assent, 
and probably even the extreme behaviorists 
in their hearts believe them,” will be inter- 
ested to observe how much of the evidence for 
Professor Woodworth’s contentions is of an 
introspective character. In his arguments on 
the nature of human motivation the appeal is 
constantly to introspection. 
MARGARET Froy WasHBurRN 
VASSAR COLLEGE 
A Laboratory Outline of Neurology. By 
C. Jupson Herrick and EnmasetH C. 
Crossy. Philadelphia and London, W. B. 
Saunders Company. 8 vo. 120 pp. 
After many years of teaching experience on 
the part of the senior author, C. J. Herrick 
SCIENCE 
[N. S. Vou. XLVIII. No. 1241 
and E. C. Crosby have produced an excellent 
laboratory outline of neurology. The outline 
includes directions for the dissection of the 
brains of elasmobranchs and of mammals. 
The directions for the elasmobranchs are es- 
pecially acceptable for they are accompanied 
by some much needed and novel diagrams 
from the unpublished work of Norris and 
Hughes. In addition to a very clear and 
well-arranged account of the subject matter, 
the volume contains abundant references to 
the literature. The text is arranged so that it 
may serve for a variety of courses, seyen of 
which are outlined in the introductory chap- 
ter. The volume is compact and well printed 
both as to text and illustrations. 
GRE 
SPECIAL ARTICLES 
HYGROMETRY IN TERMS OF THE WEIGHT OF 
A FILM OF GELATINE 
I HAVE recently had occassion to reconstruct 
a form of horizontal torsion balance which I 
used in 1890 in measuring the absolute vis- 
cosity of steel.1 Even when quite robust, it 
can easily be made so sensitive that an ex- 
cursion of over 10 em. is’ equivalent to a milli- 
gram. It should therefore be available for in- 
dicating the absorption of atmospheric vapors 
on the part of light bodies. 
Fig. 1 shows the apparatus, the suitably 
braced frame being made of strips of tin 
plate, bent C-shaped in cross section to secure 
rigidity. The torsion fiber, ab, of brass wire, 
.2 mm. in diameter 35 cm. long, is stretched 
between vertical screws (around which the 
end are wound), each provided with a lock nut 
so that a fixed tension may be imparted to the 
wire. The pointer, cd, also about 35 cm. long 
and of light varnished wood, is carried at the 
middle of the tense wire (threaded through a 
fine hole in the stem and looped around it), 
with an adjustable screw counterpoise at e in 
the rear. The index at, d, plays over a light 
circular scale of brass, fh, which in my ap- 
paratus comprehended about 130°, though it 
1 Phil. Mag., XXIX., p. 344, 1890. The change 
of the electrical resistance of gelatine in relation 
to hygrometry has been studied by Dr. G. B. Obear. 
