Viscosity of protoplasm

Figure 5. Apparent viscosity of protoplasm in Cumingia eggs as a function of temperature. Note sharp minima near 2° and 30°C and distinct maximum near 15°C. (From Heilbrunn, 1924).

The viscosity of nonliving systems (13,38) and protoplasm (81) has been so thoroughly and so often reviewed that it will be sufficient here to refer briefly to some recent work. 

Many competent investigators regard viscosity as one of the most significant of protoplasmic properties. On it, they say, do such basic activities as amoeboid movement, cyclosis, and metabolism depend but this is only indirectly true. It is contractility and not viscosity on which protoplasmic movement primarily depends the two properties are independent variables. Viscosity plays its ]iart in protoplasmic movement, but it is not a cause. If the force responsible remains constant, the rate of movement will be inversely proportional to the viscosity of the protoplasm but, if the motive force varies, the rate of flow will vary in direct proportion to it, and the viscosity need not change at all. The situation is similar in the case of metabolism viscosity plays a secondary part. Lh6risson (44) has pointed out that metabolic rate is inversely proportional to viscosity. He bases this conclusion on the fact that the rate of chemical reactions is dependent upon diffusion and rate of diffusion is proportional to viscosity. 

The structural causes of anomalous viscosity have been little discussed, perhaps because they are not generally recognized. My own interpretation, presented quite some years ago at the inaugural meeting of the Society of Rheology, is as follows non-Newtonian fluids are elastic and the structural feature responsible for the one, non-Newtonian, property is responsible for the other, elastic property (79). So far as I am aware this postulate still holds. Its full meaning will be better understood when protoplasmic structure is discussed. 

That a state of anesthesia should exist when protoplasm has been gelatinized is evident from the fact that with an increase in viscosity there must be a decrease in metabolic activity which reaches a minimum at maximum viscosity, or at reversible gelatinization of the protoplasm. Not only is metabolism, taken as a whole, slowed down by gelatinization of the protoplasm, but either the gelatinization or the anesthetic agent itself undoubtedly interferes with enzyme activity. 

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