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(1934). An equipment for the study of the physiology of the ear and of the nervous system. Acta Oto-Laryngologica: Vol. 21, No. 2-3, pp. 149-158.

An analysis has been made of the effect of ammonium and of lithium ions upon frog nerve deprived of sodium. Ammonium ions cannot substitute for sodium ions and restore the excitability of the nerve fibers; nor can they increase the L fraction of the membrane potential and the efficiency of the nerve reaction. Certain observations, however, indicate that the presence of ammonium ions outside the nerve fibers may delay the development of inexcitability in a sodium-free medium of nerve fibers restored by a moderate amount of sodium ions. Lithium ions can substitute for sodium and restore to nerve fibers of the A and C groups the ability to conduct impulses; the effect upon B fibers has not been investigated. Lithium cannot substitute for sodium in the role that sodium plays in the creation of the L fraction and in the establishment of the nerve reaction. In this respect lithium and sodium have opposite effects. This fact establishes an important difference between the two physiological responses that the nerve fibers can produce, the nerve impulse and the nerve reaction. With untreated nerve the depolarization of nerve by lithium ions at high concentrations is preceded by a phase of hyperpolarization; with nerve deprived of sodium the depolarization begins without delay.

We continue the presentation of the theory of the isolated fiber.' Effect of Saponin upon the Resting Membrane Potential.-According to reports in the literature,2 3 2 per cent saponin in Ringer's does not depolarize the internodes of isolated fibers until, after long-lasting action (20-40 min), it causes disintegration of the myelin layer. However, when, instead of a condenser-coupled amplifier which cannot detect flows of demarcation current, a d.c.-coupled amplifier is used, it is found that 2 per cent saponin is an exceedingly powerful depolarizing agent; indeed, it is stronger than 114 mM potassium chloride. The depolarization by saponin begins almost instantaneously and increases progressively during a long period of time (no less than 40-60 min). The experiments illustrated by Figures 1-3 belong to a series of 12 in which perfectly consistent results were obtained, for which reason only two experiments will be discussed in which node N, was placed in different positions. In all cases, at the end of the experiment microscopic examination (300 X) failed to detect structural changes in the treated segment, which is in agreement with the fact that in fibers of desheathed nerves kept in 2 per cent saponin for 30 min the myelin layer is stained by osmic acid in apparently the same manner as in untreated nerves. Node N, at the Center of the First Gap and Exposed N2 in the Distal Pool.-The experiment illustrated by Figure 1 is exceptional, since it is the only one in which, with node N, at the center of the first gap, an early downward peak did not appear when the amplifier was placed across the first gap (Fig. 1, 1). In all probability, the stimulation threshold in the central pool was higher than in all the other similar experiments. Nevertheless, the threshold still was low enough (cf. ref. lb) to permit the creation of an active zone in the central pool when a zero-resistance shunt was placed across the first gap (Fig. 1, 2). That the stimulation threshold was relatively high in the central pool is also proved by the fact that with the amplifier in position IV, a deflection was recorded (Fig. 1, 3) having a small downward phase and a large second upward phase (refs. 1 c, e, h). In view of the rapid action of 20 mM xylocaine (Fig. 1, 4-8), it is clear that the active zone responsible for the second upward phase was located in the distal pool. The secondary action of the anesthetic, which also developed rapidly, depressed the state of the isolated fiber. For this reason, with the amplifier across the first gap, an active zone was not created in the central pool and only a trapezoidal action potential was recorded (Fig. 1, 9). With the amplifer across the second gap, in the presence of a zero

Cocaine diffuses through the epineurium with remarkable rapidity. The coefficient of diffusion of cocaine in the epineurium cannot be less than 0.44 x 10–4 cm.2/min.; it probably is not less than 1.22 x 10–4 cm.2/min. Lack of sodium markedly sensitizes the nerve fibers to the anesthetic action of cocaine. With sodium-deficient A fibers the action of cocaine develops in two phases. During the first phase cocaine substitutes for sodium and restores to A fibers the ability to conduct impulses; during the second phase cocaine produces anesthesia. It is suggested that cocaine anesthetizes the nerve fibers through the sodium mechanism; i.e., by interfering with some of those chemical reactions in which, directly or indirectly, the internal sodium takes part.

We will try to analyze the physiological act of an animal-jump-and determine how the labyrinthine reflexes, known from experimental studies of many authors, are revealed during the jump. I hope that such an analysis will lead us to a better understanding of the physiology of the labyrinth, as we will find out the purpose of the reflexes.

One of the most important problems related to sensing and measurement techniques is the presence of high level common mode signals superimposed on the differential signals of interest. Commonly, high common mode rejection ratio differential amplifiers are used requering a high input impedance so as to attenuate, said, undesirable signals and furthermore to make difficult the associated current flow through the ground loop present in such systems. The implementation of equipment based on these criteria requires, generally, the use of high performance, and thus high cost components. The sensing and measurement procedure proposed in the present paper is based on the use of a capacitor that is equivalent to an analogic storage element and that, in a first switching mode, is connected across the measurement points, while it is disconnected from the differential amplifier input terminals. In a second switching mode, the capacitor, holding the voltage sample sensed, is disconnected from the sensing points and is connected to the differential amplifier inputs in which output the amplified signal will appear. Furthermore, the proposed system is quite suitable for accepting microprocessor generated switching pulses, the microprocessor sampling directly the signal for converting it into the digital code in the usual mode.

Two retrocecal and extraperitoneal appendix cases are showed. Atypical clinical signs, slow evolution, perforation and abscess were found. Radiological diagnosis is based by seeing the calculus and the appendix by means of barium enema. When appendix calculus is demonstrated and clinical signs are present, a surgical operation must be order urgently. Profilactic appendicectomy is recommended when no symptoms.