H. L. White

A COMPARISON OF THE ELECTROPHORETIC MOBILITIES AND SEDIMENTATION VELOCITIES OF RED CELLS FROM NORMAL AND PREGNANT HUMAN SUBJECTS.

It has long been known that the extent to which red cells aggregate (as measured by sedimentation velocity) in their own plasma varies greatly with the species. Also, within one species (human) the degree of aggregation varies with the physiological or pathological state of the individual, being greatly increased above the normal during pregnancy and in many febrile and neoplastic disorders. It has recently been shown (1) that the main cause of species variations in sedimentation velocity is a difference in the red cells themselves, rather than in the plasma, since cells from various species sink at very different rates in a common medium such as 1 per cent gelatin. This species difference is correlated, 1, with the electrophoretic mobility of the red cells, the cells which settle most rapidly having the highest mobility at pH 7.4, 2, with the isoelectric point, the cells with highest sedimentation velocity having the lowest isoelectric point, and, 3, presumably with the chemical composition of the red cell surface, those cells sinking most rapidly which have the highest proportion of lipoid to protein with a resultant higher interfacial energy. The increased rate of sedimentation accompanying pregnancy and pathological conditions in man, on the other hand, has long been assigned to an increase in the globulin and particularly in the fibrinogen fraction of the plasma. That an increase in plasma globulin takes place during these conditions has been repeatedly demonstrated; that such an increase in globulin concentration will directly affect the sedimentation velocity of the red cells is equally certain (2). The possibility of a difference in the cells of slowly and rapidly settling human blood comparable to that observed in different species has

ELECTROLYTIC RESISTORS OF HIGH RESISTANCE

Resistances of from 1×108 to 3×1010 ohms have been obtained by sealing capillary bridges (inside diameter 0.005 to 0.088 mm) between calomel electrodes made up with dilute KCl—saturated calomel solutions. These resistors can be used satisfactorily with an electrometer or sensitive galvanometer and condenser set‐up. They do not exhibit polarization and their resistances do not change with age. The temperature coefficient is that of the KCl solution used in the preparation of a resistor.