CHAPTER IV 



VISCOSITY MEASUREMENTS 



L. V. HeilbRUNN, University of Pennsylvania 



A. Introduction 107 



B. Viscosity Concept 109 



C. Viscosity of Blood 110 



D. Viscosity of Protoplasm Ill 



1 . Gravity and Centrifuge Methods 112 



2. Brownian Movement Method 121 



E. Results Obtained from Viscosity Study 125 



F. Possibilities for the Future 127 



References 129 



A. INTRODUCTION 



There are two chief reasons that a biologist or a biophysicist might 

 be interested in viscosity measurement. He might want to know 

 something about the condition of flow of the circulating fluids of an 

 organism. He would then seek to determine the viscosity of the 

 blood or the lymph. Such determination can be made rather simply 

 with ordinary physical methods not peculiar to the student of bio- 

 logical phenomena. A much more difficult problem is the determina- 

 tion of the viscosity of the protoplasm within the cells of an organism. 

 The fact that protoplasm is a colloid and as such is subject to sudden 

 and sharp changes in viscosity makes it obvious that the student of 

 cell mechanics should acquire what information he can about the 

 viscosity of the protoplasm and how this viscosity changes during the 

 life and death of the cell. No other physical property of the proto- 

 plasm offers as much hope for the interpretation of vital mechanics as 

 does the viscosity. A cell may become violently active or may lose 

 its activity; it may become poisoned, electrocuted, or crushed and 

 yet such physical properties as specific gravity, electric potential at 

 the surface, or birefringence may scarcely be affected. Not so the 

 viscosity. A dividing cell goes through an entire cycle of protoplasmic 



107 



