The Viscosity of the Plasmagel of Amoeba proteus at Different Temperatures

Abstract

C OLLOIDAL materials show a wide range of variation in their relation to temperature. In some colloidal solutions an increase in temperature is accompanied by a sharp decrease in viscosity as the solution changes from the state of a gel of high viscosity to the state of a sol of low viscosity. However, the viscosity of many colloidal solutions diminishes more or less gradually with a rise of temperature; such solutions are relatively fluid at all ordinary temperatures. The colloids of a living system may show a behavior which is unlike that of inanimate materials in general. Thus Heilbronn (1922) found that the protoplasm of the slime mold Reticularia passed through a maximum viscosity as the temperature was raised. Similar results were obtained by Heilbrunn for the protoplasm of Cumingia eggs (1924) and also for Amoeba dubia (1929). In other cases the behavior of the protoplasmic colloid corresponds more nearly to that of inanimate materials, in that a progressive decrease in viscosity has resulted from a rise in temperature. This type of behavior has been reported by Faur&-Fremiet, F. and G. Weber, and Pantin. References to these authors, as well as a more complete review and discussion of the literature, may be had by referring to a monograph by Heilbrunn (1928). In the present experiment the method employed for the determination of viscosity was the centrifuge method as used by Heilbrunn (for references see Heilbrunn, 1928). The centrifuging was done on the high speed of an old model Bausch and Lomb hand centrifuge, which was turned at the rate of one turn per second. At this speed there was developed a centrifugal force 4,084 times gravity. In order to arrive at a relative measurement of the viscosity, a scale of arbitrary units was selected in the following manner. When amoebae 246 [PHYSIOLOGICAL ZOiLOGY