VISCOSITY OF PROTOPLASM 295 



semi-liquid solution of Protein we may also assume that any condition 

 tending to alter the consistency of the interstitial protein solution would 

 deform the structure of the emulsion. Coagulating Agents especially 

 might be expected to reduce the interstitial gel to discrete granules or 

 separate flocculi, thus removing the obstacle to coalescence of the fat 

 globules and the consequent coarsening of structure and widening of 

 interstices. Corresponding to this conception we find that simple 

 heating of a piece of frog's skin renders it freely permeable to water 

 in either direction, instead of only in one. The effect of coagulating 

 agents' upon permeability may also be strikingly illustrated in the 

 following way: If paramcecia be washed free from culture medium 

 with pure distilled water and suspended in a solution of Methyl Green 

 (free from methyl violet), the protoplasm of the infusorians takes on a 

 faint greenish tinge, but the large pseudo-nucleus remains white and 

 unstained. After removing the excess of methyl green by washing the 

 organisms in distilled water, a little Cupric Chloride may now be added 

 to the water. Immediately the nucleus becomes stained a deep green, 

 indicating that the impenetrability of the nuclear membrane for the 

 dye prevents it from being stained in the normal cell, but after the 

 action of this protein coagulant, which kills the organisms, the permea- 

 bility of the nuclear membrane is so enhanced that the dye can readily 

 enter and even attain a greater concentration therein than it does in 

 the cytoplasm. 



THE VISCOSITY OF PROTOPLASM. 



The major part of the high degree of Viscosity which protoplasm 

 displays is attributable to the Protein which it contains. The viscosity 

 of a protein solution increases very rapidly indeed with its concentra- 

 tion, so rapidly, in fact, that earlier observers were inclined to the 

 belief that the viscosity changed suddenly at definite critical con- 

 centrations instead of changing evenly and with regularity as it does 

 in solutions of crystalloids. Later observations have shown us, how- 

 ever, that the viscosity of protein solutions increases with the concen- 

 tration in accordance with the usual formula ~ = A n , where 77 is the 



viscosity of the solutiorr, 170 that of the solvent, n the concentration of 

 the solution and A a constant, the numerical value of which depends 

 upon the nature of the dissolved substance, and upon the temperature. 

 The following are results obtained by Sackur, employing Sodium 

 Caseinate : 



n (in equivalents - (15 C.). logio A. 



of sodium) . % 



0.01830 1.870 14.8 



0.01370 1.581 14.5 



0.00915 1.363 14.3 



0.00547 1.202 14.6 



0.00458 , 1.165 14.5 



