Electro-physiology electrophysiolog00brub Year: 1894 B-10 BRUBAKER. out to a tine capillary point. 'I'lie tube is filled with niercuiy and its capillary point immersed in a 10-per-cent. solution of sulphuric acid. The vessel containing the acid is filled to the exteiit of several millime- tres with mercury also. The mercury in the tube is put in connection with a platinum wire (a), and the acid in the vessel with a second wire (6), When a constant current passes into the apparatus in the direction from 6 to a the mercury is pushed up the tube, and, upon the breaking of the current, it may or
Electro-physiology electrophysiolog00brub Year: 1894 B-10 BRUBAKER. out to a tine capillary point. 'I'lie tube is filled with niercuiy and its capillary point immersed in a 10-per-cent. solution of sulphuric acid. The vessel containing the acid is filled to the exteiit of several millime- tres with mercury also. The mercury in the tube is put in connection with a platinum wire (a), and the acid in the vessel with a second wire (6), When a constant current passes into the apparatus in the direction from 6 to a the mercury is pushed up the tube, and, upon the breaking of the current, it may or may not return to the zero-point. For the purjiose of measuring in millimetres of mercury the pressure necessary to compensate this change in the capillary constant produced by the elec- tro-motive force of polarization, the apparatus is provided with a pressure- vessel, H, and a manometer, B. This electrometer can be applied to any Fig. 5.—Capillary Electrometer. microscope having a reversible stage. The oscillations of the mercury can then be observed with the microscope provided with an ocular microme- ter. The special advantage of the electrometer is, that it will respond instantly to any variation in the electro-motive force, and indicate a dif- ference of potential, according to Lippmann's observation, as slight as t*'^ T5^?TT of a Daniell. These rapid oscillations can be recorded by photographic methods. Electrodes.—It is essential, in the detection of weak electrical cur- rents with highly-sensitive galvanometers, that the electrodes, which are placed in contact with the tissues, should not only be absolutely homo- geneous, as the slightest diflference between them will develop a current upon the closure of the circuit, but that they should also be incapable
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