﻿INSTITUTE OF PHYSIOLOGY
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Fig. 10.—Galvanometer Room
the poles of 30.000 gauss. For normal electrocardiograph work we do not need such a strong field, but it is very useful for all kinds of finer work. A small Edelmann electrocardiograph with a double permanent magnet is employed for different electrocardiographic work upon cold-blooded animals.
The department comprises further two rooms where all other kinds of electrophysiological work can be done. Here we arranged apparatus to determine the chronaxia of tissues and organs. Special mention should be made of a chronaximeter of our design that allows control for a very short duration of time (1/200.000 of a second) necessarçr for excitation. A falling weight breaks successively a shunt and a main current is employed for the excitation of tissue. The excitation-time between those two events is controlled by measuring by means of a ballistic galvanometer the remaining charge on a condenser of which are broken successively the feeding current and the shunt.
Another room has been reserved for spectrographic work. Absorption spectra of liquids are made by photographing through a layer of the liquid a source of ultraviolet light by means of a quartz-spectrograph of Hilger. The absorption spectrum obtained in this manner is analyzed and transformed in a curve. Light condensed on the photographic plate containing
the spectrum falls upon a series of very fine thermocouples and develops an electric current which is registered by means of a galvanometer upon photographic paper fixed upon a drum. The movements of the plate and use of the drum are coupled. Each raj’ or each darkening of the photographic plate will change the height of the curve, so that the changes produced by absorption are immediately visible in the curve.
DEPARTMENT FOR RESEARCH UPON COLDBLOODED ANIMALS
On the north, close to the refrigerating room on the other side of the corridor is situated the department for research on cold-blooded animals. This place has been chosen because it is very cool in summer and not too cold in winter so that the daily variation of temperature in both seasons is reduced and rather small.
One room is fitted out as a more special laboratory with cupboards, and with free and fixed tables before the windows. The other room contains the large basin for winter quarters of frogs (2 by 2 meters) and a large aquarium (2.10 by 1.35 meters and 0.85 meters deep) for fishes. Both are supplied by a constant stream of water.