capacity bridge, 1-A
Dateearly 20th Century
Inventory NumberRS0122
ClassificationBridge
Subject
Maker
Western Electric Company
1869 - 1995
Cultural Region
Dimensions17 x 27 x 21 cm (6 11/16 x 10 5/8 x 8 1/4 in.)
Material
Accessories2 small keys.
DescriptionA Western Electric-Cruft 1-A capacity bridge with bakelite knobs in a wooden box with brass hardware and leather handle.
Signedetched and white filled on top panel: 1-A CAPACITY BRIDGE / SERIAL No. 31106
plate on top of lid: 1-A CAPACITY BRIDGE / TRADE MARK / Western Electric / REG. U.S. PAT. OFF. / MADE IN U.S.A.
FunctionPossible function: www.jgp.org/cgi/reprint/12/1/37.pdf
ELECTRIC IMPEDANCE OF SUSPENSIONS OF ARBACIA
EGGS.
BY KENNETH S. COLE.*
(From Cruft High Tension Electrical Laboratory and the Laboratory of General
Physiology, Harvard University, Cambridge.)
(Accepted for publication, April 23, 1928.)
In work done several years ago on the heat production of the Arbacia
egg at fertilization and during early development (11) the suggestion
was made that the phenomena observed might be due to changes in the
cortex. Inasmuch as the heat data can give no clue to the action of
component parts of the egg, another means of analysis was sought
which might give an answer to the various questions raised. The work
of Fricke and Morse (3) and Philippson (10) suggested that the impedance
of suspensions of eggs to various frequencies of alternating
current might yield valuable facts regarding the electric capacity and
resistance of the surface of the egg, and the resistance of the interior,
and the changes of these three quantities at fertilization and during
development.
Apparatus.
Although it was first planned to use a capacity bridge to measure
both the resistance and the capacity of the suspensions of Arbacia eggs
it was found after considerable work that the bridge had severaI very
serious defects for this particular work. In the first place it became
very complex as the range of frequencies to be investigated was extended
(3). This made it necessary to devote an undue amount of
time to the taking of each reading and the changing from one frequency
to another. In the second place, unless one were willing to go to the
very ultimate in amplification it was necessary to use an undesirably
high current density in the electrolytic cell.
ELECTRIC IMPEDANCE OF SUSPENSIONS OF ARBACIA
EGGS.
BY KENNETH S. COLE.*
(From Cruft High Tension Electrical Laboratory and the Laboratory of General
Physiology, Harvard University, Cambridge.)
(Accepted for publication, April 23, 1928.)
In work done several years ago on the heat production of the Arbacia
egg at fertilization and during early development (11) the suggestion
was made that the phenomena observed might be due to changes in the
cortex. Inasmuch as the heat data can give no clue to the action of
component parts of the egg, another means of analysis was sought
which might give an answer to the various questions raised. The work
of Fricke and Morse (3) and Philippson (10) suggested that the impedance
of suspensions of eggs to various frequencies of alternating
current might yield valuable facts regarding the electric capacity and
resistance of the surface of the egg, and the resistance of the interior,
and the changes of these three quantities at fertilization and during
development.
Apparatus.
Although it was first planned to use a capacity bridge to measure
both the resistance and the capacity of the suspensions of Arbacia eggs
it was found after considerable work that the bridge had severaI very
serious defects for this particular work. In the first place it became
very complex as the range of frequencies to be investigated was extended
(3). This made it necessary to devote an undue amount of
time to the taking of each reading and the changing from one frequency
to another. In the second place, unless one were willing to go to the
very ultimate in amplification it was necessary to use an undesirably
high current density in the electrolytic cell.
Historical AttributesCruft
Western Electric Company
Accessories: 2 small keys.
Object number: RS0127
Western Electric Company
Accessories: 2 small keys for the lock attached with wire loop.
Object number: RS0125
Western Electric Company
Date: early 20th Century
Object number: RS0146
E. Hartnack & A. Prazmowski
Date: circa 1880
Accessories: objectives in green leather box (5): 2, 4, 6, 7, and unmarked; objectives in brown box (2): 2, 3; oculars (5); 1, 2, 3, 4, 5; polarizing eyepiece and substage apparatus; substage condenser; substage cup diaphragms (4); slider with sleeve to hold substage accessories; large bull's eye condenser with stand; aperture-stop rotating wheel; blue filters (3); flat case; case keys (2).
Object number: 1145a
William J. Murdock Company
Date: 1910-1950
Object number: RS0163
Western Electric Company
Date: early 20th Century
Object number: RS0139
