Abstract
Instruments for the measurement of tissue and cell respiration have steadily moved, since the introduction of Warburg's convenient manometer, in the direction of smaller volume and greater sensitivity. Gerard and Hartline 1 took advantage of the greater stability afforded by reducing the tissue chamber of a volumeter to capillary dimensions (0.5 to 1.2 mm diameter) and having this inside the relatively large “differential” chamber. Index drop movements, followed with an ocular micrometer, were consistent over 5-minute intervals, even when corresponding to volume changes of about 0.01 cmm. The diver technique, introduced by Linderström-Lang, 2 , 3 is of the same order of sensitivity and consistency; and the electrical method 4 gives promise of superior performance.
We have further developed the capillary method so that it is convenient to follow the respiration of 10 tissue samples at once, and it is possible to measure absolute gas volume changes of 0.001 cmm, minute by minute, with an error of some 8% minute by minute, under 1% for longer intervals. The respiration even of bits of frog sciatic nerve weighing a fraction of a milligram can thus be followed at half-minute intervals.
The tissue chamber, also containing filter paper bits soaked with acid or alkali and separated from each other and the tissue by dry paper guards, is a short length of capillary of 1.2-1.5 mm internal diameter. The “open” end of this, after the insertion of materials, is plugged with plasticine. Into the other end has been cemented a fine drawn capillary of about 0.2 mm diameter. At the close of the experiment, this capillary is broken off and its end diameters accurately measured by end on examination with an ocular micrometer.
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