Excitation characteristics of the squid giant axon: a test of excitation theory in a case of rapid accommodation

1. The characteristics of the threshold excitation behavior of the squid giant axon were investigated with condenser discharges, exponentially blunted D. c. shocks, sinusoidal currents, and brief condenser-discharge test shocks superimposed at either electrode at controlled brief intervals following the closing of a constant current. 2. Data obtained by the use of condenser discharges and exponentially blunted currents followed theoretical patterns separately, but could not be mutually reconciled, under the system of the two-factor theories of excitation, since the accommodation was so rapid that the apparent ratio between the two time factors was incompatible with certain previously neglected theoretical limitations. 3. Data obtained with the other procedures indicated similarly rapid accommodation, but usually showed an imaginary component in the values of the time constants, associated with a capacity of the threshold to exhibit damped oscillatory behavior. 4. The anodal threshold behavior did not parallel that at the cathode, showing neither oscillation nor accommodation at ordinary current intensities. 5. The digressions from predictions of the two-factor theories of excitation are partly analyzed and compared with other reported deviations.     

The mechanism of glucose transfer into and out of the human red cell

1. The kinetics of the movements of glucose in both directions across the surface of the human red cell were studied by optical recording (Ørskov method) of resultant cell volume changes. 2. A wide experimental variety was arranged in the relations between the several quantitative factors contributing to the glucose gradient and the volume changes expected, in order to provide a maximum variety of systematic relations between those factors and the rate of glucose transfer. 3. The kinetics were shown to follow the patterns predicted on the basis of a simple carrier system, involving formation of a highly undissociated complex between the sugar and some factor in the cell surface, provided the glucose concentrations used did not exceed about 3/4 isosmotic. Certain simple properties of this system are derived from the data. 4. At very high glucose concentrations, this system apparently gradually fails to operate; this failure is reversible upon lowering of the excessive glucose concentration. 5. An empirical correction was derived for a previously known but uncalibrated optical disturbance complicating the use of the Ørskov method with media containing appreciable concentrations of non-electrolytes.