PHYSICS: TOLMAN AND STEWART 
189 
mecium, and the cutting is due to constriction in this ring, and the 
constriction to a change in surface tension, the work invo ved would 
require a minimum reduction along the inner surface of the ring of at 
least 383 dynes per centimeter. 
The bulk of evidence at hand seems to indicate that the paramecia 
are divided by the approach of two pseudopods and not by the con- 
striction of a ring. To account for the process on the basis of the sur- 
face tension theory, therefore, the surface tension of the amebae would, 
in all probability, have to be considerably higher than 1118 dynes per 
centimeter. The surface tension of protoplasm is, however, only ap- 
proximately 50 dynes per centimeter. It is, therefore, probably at best 
an insignificant factor in the process of feeding in Ameba. 
More detailed descriptions of these observations and calculations will 
be published elsewhere. 
The following references may be listed: 
BUtschli, O., 1892, Untersuchimgen iiher mikroskopische Schaume und das Proto plasma, 
Leipzig, 234 S. 
Jensen, P., 1905, Zur Tlieorie der Protoplasmabewegung und uber die Auffassung des 
Protoplasmas als chemisches System. Anat. Hefte, Wiesbaden, 27, Heft 83, 831-858. 
McClendon, J. F., 1912, The Osmotic and Surface Tension Phenomena of Living Ele- 
ments and their Physiological Significance, Biol. Bull., 22, 113-204. 
Rhumbler, L., 1905, Zur Theorie der Oberflachenkrafte der Amoben, Zs. wiss. ZooL, 
83, 1-52. 
, 1910, Die verschiedenartigen Nahrungsaufnahmen bei Amoben als Folge ver- 
schiedener Colloidalzustande ihrer Oberflachen, Arch. Entw.-Mech., 30, 194-220. 
Ryder, J. A., 1893, Dynamics in Evolution, Biological Lectures, Woods Hole, pp. 63-81. 
Verworn, Max, 1909, Allgemeine Physiologic, Fiinfte Auflage, Jena, 742 S. 
THE ELECTROMOTIVE FORCE PRODUCED BY THE 
ACCELERATION OF METALS 
By Richard C. Tolman and T. Dale Stewart 
DEPARTMENT OF CHEMISTRY. UNIVERSITY OF CAUFORNIA 
Received by the Academy, March 2, 1916 
Modern theories of electricity have led to the belief that the passage 
of an electric current through a metal really consists in the progressive 
motion of *free* electrons contained in the body of the metal itself. If 
this be true we may now expect a number of effects arising from the 
mass of these electrons which were not predictable on the basis of older 
theories which thought of electricity as a sort of intangible massless fluid. 
As examples of such effects, we should expect the rear end of an accel- 
erated rod of metal to become negatively charged owing to the lagging 
behind of the relatively mobile electrons which the metal contains, 
