126 L. V. HEILBRUNN 



tation and in clinical practice, no measurements of blood viscosity are 

 made. 



It is obvious that any increase in blood viscosity would impose an 

 added strain on the heart, and this may be an important factor in 

 some types of distress or disease. 



Studies of protoplasmic viscosity have given far more interesting 

 results than studies on blood viscosity. Earlier biologists and physi- 

 ologists were forced to guess as to the changes in viscosity and colloidal 

 state. Muscle contraction was thought by some to involve a sharp 

 increase in protoplasmic viscosity — a gelation — whereas others de- 

 cided on the basis of reasoning alone that muscle protoplasm changed 

 from a viscous and elastic gel to a fluid sol when it was made to con- 

 tract. Similarly, in other processes, such as cell division, changes 

 in viscosity were assumed rather than measured. The action of 

 drugs was explained in terms of viscosity change. Thus Claude 

 Bernard beheved that ether and chloroform produced their effect by 

 causing a semicoagulation of the protoplasm. 



The introduction of correct methods of protoplasmic viscosity 

 has replaced the earlier speculations with definite facts. A summary 

 of this factual information is given by Heilbrunn {1,15). As already 

 noted, some types of protoplasm have a low viscosity. The values 

 of the absolute viscosity of such protoplasm are approximately 3-5 

 centipoises. This is the viscosity of the nongranular protoplasm 

 The viscosity of the entire protoplasm, granules and all, depends on 

 the concentration of the granular suspension. In the sea urchin egg, 

 the entire protoplasm has a viscosity several times as great as that 

 of the hyaline protoplasm. But, where the concentration of granules 

 is very high, the viscosity of the entire protoplasm may be very great. 

 Thus in Paramecium protoplasm, the protoplasmic viscosity may be 

 several thousands of centipoises. 



The interior protoplasm of a cell may have a low viscosity, whereas 

 the cortical region of the cell may have a very high viscosity, even ap- 

 proaching infinity. This outer cortex may be very thin, as in some 

 marine eggs, or it can be much thicker, as in the common Amoeba. 

 Perhaps in some cells essentially the entire protoplasm has the prop- 

 erties of a cortex. 



In Amoeba, the high viscosity of the cortical protoplasm seems to 

 depend on the presence of calcium there. If this calcium is in part 

 removed by sodium or ammonium oxalate, the viscosity of the cortex 

 decreases sharply, and a similar decrease occurs if the calcium of the 

 cortex is replaced by potassium as a result of ion exchange. 



