American journal of physiology . to such points is very necessary in the technique of electro-physiology. A long narrow test tube is half filled with water, and the waterboiled. A portion of the end of the nerve is then, brought in con-tact with the wall of the test tube, which is held at an angle, withthe mouth away from the nerve, so that no hot water vapor willinjure the rest of the nerve. A few millimetres of the end of thenerve can thus be thoroughly cooked; a scissor section is thenmade through the coagulated portion in case it is too long. Witha millimetre or two of cooked tissue on the
American journal of physiology . to such points is very necessary in the technique of electro-physiology. A long narrow test tube is half filled with water, and the waterboiled. A portion of the end of the nerve is then, brought in con-tact with the wall of the test tube, which is held at an angle, withthe mouth away from the nerve, so that no hot water vapor willinjure the rest of the nerve. A few millimetres of the end of thenerve can thus be thoroughly cooked; a scissor section is thenmade through the coagulated portion in case it is too long. Witha millimetre or two of cooked tissue on the end of the nerve thedemarcation current remains for a long time without decrease, e. one experiment at the end of the first hour the demarcation cur-rent had fallen from 84 to ^6 mm., at the end of the second hour to59 mm. Care must of course be taken not to injure the remainderof the nerve, and also to make the thermal section clean, which isbest done by holding the nerve perpendicular to the test tube. 14 J. C. After the non-polarizable electrodes had been prepared and put inposition in the nerve chamber, a Hgature of silk thread was passedaround the distal end of the nerve, and tied to a thin piece of strawwhich served as a needle for threading the nerve through the tun-nel. In order to accomplish this most easily the tank was removedfrom its base. The proper precautions were taken for moisture byproviding a liberal supply of wet filter paper. After the nerve was in position, the water supply was turned onand adjusted. We may call the stream flowing through the tankand the two tubes on either side of the heater the tank supply, the current passing throughthe heater the heatersupply. Both streams werecopious, so that the readingsof the thermometers (indi-cated in Fig. 3) representedvery closely the temperatureof the water passing aroundthe tunnel. The demarca-tion current was read (nocompensation was used),and then the nerve wasstimulated with variousstrengths
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