TIA 
in a sense, solid not liquid; but as it is made 
up of atoms joined into the molecular mesh- 
work only by their mutual chemical affinities, it 
is possible for various physical agents to inter- 
rupt the continuity of the mass and to make it 
act somewhat in the manner of a liquid, to be- 
come subject to surface tension laws, etc. The 
solidity is not that of cohesion, but only the re- 
sult of the chemical attractions that tend to 
hold together the elements in the complex 
molecular net against forces that might tend to 
disturb the continuity. 
A cell is a continuous net work made of 
molecules joined in chains ; the members of the 
chains are different within the nucleus from 
those outside the nucleus, but there is no break 
in continuity from one region to the other. 
Approaching the problem from the physiolo- 
gist’s point of view, the author devotes his dis- 
cussion chiefly to phenomena of nerve, muscle, 
and electrical organ. A nerve is conceived as 
containing rows of living, conductive molecules 
surrounded by various liquid and emulsive sub- 
stances. Each component molecule is joined 
to its fellows in the row by the affinity of some 
of its atoms. Progressive chemical action be- 
tween successive molecules in the chain and 
the environing materials constitutes the change 
that travels as a nerve impulse. 
In muscle similar chains of conducting mole- 
cules have connected with them, as additional 
mechanisms, special contractile molecules, which 
owe their change of shape to chemical rear- 
rangements. 
Electrical organs easily lend themselves to 
an application of similar diagrammatic formula- 
tions. 
Strange as it may seem the phenomena of 
the active flowing of protoplasmic streams in 
those exceptional water-plants, Stoneworts, are 
made foundation stones in the author’s attempt 
to realize protoplasm as a solid, continuous, 
gigantic molecule. His previous valuable con- 
tribution to the physiology of these plants 
(Studien tber die Protoplasmastrémung bei 
den Characeen. Jena, Gustay Fischer. 1898) 
resulted in the discovery of marked agreement 
in the conductive mechanisms in nerve, muscle 
and the cells of Nitella syncarpa. The motor 
mechanism in the last, however, he concludes, 
SCIENCE. 
[N. S. Vou. X. No. 256. 
is different from that in muscle. Both the con- 
stant rotation of the moving layer of proto- 
plasm and the very remarkable separate rota- 
tion of separate chlorophyll grains, which the 
author is sure he has seen, are conceived of as 
results of successive making and breaking of 
chemical union along the surface of contact of 
moving and non-moving protoplasm. 
EK. A. ANDREWS. 
JOHNS HopKINS UNIVERSITY. 
A Dictionary of Birds. By ALFRED NEwToN, 
assisted by Hans GADow. Cheap issue, un- 
abridged. London, Adam and Charles 
Black. 1893-96. Pp. xii+ 1088. Price, 
$5.00. 
Good wine needs no bush and Newton’s Dic- 
tionary of Birds needs no recommendation, the 
more that it was fully reviewed in SCIENCE upon 
its first appearance. 
There are, however, many who will welcome 
this edition, not only for its greatly reduced 
price, but for its convenient size, since without 
sacrificing a word of the text the use of thin, 
but good paper, makes this book a compact 
volume. Few there are who have Professor 
Newton’s wide acquaintance with the literature 
of ornithology and the bibliographical references 
alone are sufficient to make the work a neces- 
sity, not only in the library of the working 
ornithologist, but of the general reader, while 
the contributions of Dr. Gadow constitute a 
text-book on the anatomy of birds. Our 
younger ornithologists will do well to keep this 
book within reach and consult it often, if only 
to fully appreciate that scientific facts may be 
presented in the best literary form. 
Ry AC 
BOOKS RECEIVED. 
A Treatise on Crystallography. W. J. LEWIS. 
bridge, England, University Press. 1899. 
xxii-+612. 14s. 
The Strength of Materials. J. A. EWING. Pp. xii ++ 
246. Cambridge, England, University Press. 1899. 
Pp. xxii+612. 12s. 
Electric Wiring, Fittings, Switches and Lamps. W.- 
PERREN MAycock. London, Whittaker & Co.; 
New York, The Macmillan Co.’ 1899. Pp. xv+ 
446. $1.75. 
Cam- 
Pp. 
