SUMMARY OF CURRENT RESEARCHES RELATING TO 
310 
Apart from an account of liis own experiments, Biitschli gives an 
historical and critical account of the various interpretations of protoplas- 
mic structure, e. g. those of Flemming, Schneider, Altmann, Fayod, and 
Kiinstler, and of protoplasmic movement, e. g. those of Hofmeister, 
Engelmann, Leydig, Berthold, and Quincke. The author’s general 
conclusion is that protoplasm has a frothy or foam-like structure, and 
that the physical conditions observable in the bubbles of the artificial 
foams do mutatis mutandis help us towards an understanding of the 
streaming movements and changes of shape in protoplasmic units. It 
need hardly be said that Biitschli does not claim to have made “ artifi- 
cial protoplasm.” His work has rather been to demonstrate analogies 
of structure and activity between living and not-living matter ; and 
while it may remain a matter of opinion whether he has really brought 
us nearer an understanding of a vital movement, it will at least be 
conceded that the task of eliminating all that can be at present physi- 
cally explained is useful, and that his work, with its carefulness of 
observation and ingenuity of experiment, is full of suggestiveness. 
y. G-eneral. 
Movement of Living Matter.* — Dr. Max Verworn thinks that the 
problem of vital movement is to be studied most successfully in Rhizo- 
pods. To begin with striped muscle is to begin at the wrong end. All 
the theories of Hofmeister, Engelmann, Hermann, and others are partial 
at best. Verworn begins with the formation of pseudopodia, as seen for 
instance in Orbitolites complanatus. In an active protrusion the plasmic 
streaming is wholly centrifugal ; when protrusion ceases a centripetal 
back-flow sets in ; in retraction this is the only movement. Cut an out- 
flowing process, the stimulated protoplasm begins to stream centripetally, 
and, both as a whole and in its parts, tends to form spheres. Cut a 
piece off altogether ; for a time it may give forth pseudopodia, but soon it 
begins to degenerate, and the phenomena of degeneration are identical 
with those of an individual persistently stimulated to retraction. 
The movement is either an expansion or a contraction. In the phase 
of expansion there are local lessenings of the surface tension. But what 
is the condition of a diminution of the surface tension before the expansion 
of the plasmic sphere ? The chemical affinity of the protoplasm for oxygen 
is the condition. As Kuhne showed long ago, the exclusion of oxygen 
inhibits the protrusion of pseudopodia. It comes to this, that the 
plasmic particles are drawn within the operative sphere of the oxygen 
molecules in the medium, and being satisfied remain indifferent, or are 
shoved aside by their successors. This may be called, if we please, 
chemotropism. The fact that the unit organism is not or may not be 
homogeneous, explains why pseudopodia are protruded here and there, and 
not over the whole surface. So much for expansion. Contraction, on 
the other hand, is an expression of increased surface tension. This 
occurs when the satisfied plasmic particles, forming highly complex 
explosible combinations, break up on being stimulated. This involves 
profound chemical changes, and the stimulated disrupted particles are 
drawn to the centre of the unit mass. The condition of the now 
* ‘ Die Bewegung der lebendigen Substanz. Eine vergleichend-physiologische 
Untersuchuug der Kontraktionsersoheinungen,’ Jena, 1892, 8vo. 
