VISCOSITY 215 



plasm because the particles are suspended in minute vacuoles 

 the contents of which are of low consistency, the vacuoles 

 themselves being embedded in a firm jelly, viz., the living proto- 

 plasm. While these facts make it necessary to use Brownian 

 movement as an indicator of protoplasmic viscosity with caution, 

 they do not altogether nullify the observations that have been 

 made by this method, because not all cell particles are in vacuoles; 

 many are suspended in the protoplasm. 



In a quiet Amoeba, the number of particles in motion, which 

 are suspended directly in the protoplasmic matrix {i.e., not in 

 vacuoles), are few, and the amplitude of their motion is small. 

 The viscosity of the protoplasm is, therefore, high. The con- 

 sistency of glycerin is just high enough to prevent the motion 

 of suspended carmine granules. The latter approximate the 

 dimensions of protoplasmic particles; therefore, the viscosity 

 of the quiescent protoplasm of Amoeba is somewhat less than 

 that of glycerin, i.e., between seven and eight hundred times 

 that of water. In an active Amoeba, all particles, except the 

 largest droplets, are in motion. The viscosity of the protoplasm 

 is then low. 



Bayliss used Brownian movement as an indicator of the sol 

 and gel state of Amoeba when the latter is subjected to an electric 

 shock. The electric shock causes the protoplasm to gelate, 

 and all Brownian movement of particles ceases. When Amoeba 

 recovers, the protoplasm solates, and the particles again take 

 up their active motion. 



W. H. Lewis finds that Brownian movement may be present 

 or absent in tissue-culture cells, indicating considerable variation 

 in the consistency of the cytoplasm, ranging from "fluid" to 

 "semisolid." Particles in the cells of smooth and skeletal muscle 

 exhibit little movement and in heart muscle none at all. 



Bass-Becking has made a mathematical analysis of the Brown- 

 ian movement of particles in Spirogyra and finds that the con- 

 sistency of the protoplasm of this alga varies from that of water 

 to several hundred times that of water, all within a very small 

 region. He concludes that protoplasm has no single viscosity 

 value but a large number of variable viscosities. 



The Electromagnetic Method. — Several workers have at- 

 tempted to determine the consistency of protoplasm by the 

 electromagnetic attraction of a metal particle embedded in it. 



