3 6 4 



HOTAXICAL GAZETTE 



[NOVEMBER 



scale, but give in addition viscosity values to each degree of 

 consistency. These values are directly referable to definite concen- 

 trations of a dispersion (colloidal solution) of gelatine, each con- 

 centration, as nearly as could be determined, having the same 

 consistency as that of the protoplasm which has been given a 

 corresponding viscosity value. The gelatine used is a commercial 

 one and readily obtained. 5 



Examination of the gelatine dispersions was done at room 

 temperature (i8° C.) in the moist chamber of the microdissection 

 instrument, with needles identical with those employed for the 

 dissection of protoplasm. Table I shows the viscosity values and 



TABLE I 



Viscosity 

 value* 



I 



2 



3 



4 



5 

 6 



7 

 8 



9 



io 



Descriptive term 



Watery 

 Very liquid 

 Liquid 



Slightly viscous 

 Rather viscous 

 Decidedly viscous 

 Very viscous 

 Extremelv viscous 

 Gel 

 Rigid gel 



Percentage of 

 gel at in ef 



O.o 

 O.05 

 0.2 

 0.4 



0.6 

 0.7 



0.8 



1.0 



2.0 



Substances having an 

 equivalent viscosity^ 



Water 



Paraffine oil 



Glycerine 

 Bread-dough 



Vaseline 

 Firm gelatine 



*The abbreviation v. v. will be used for viscosity value. 



t A 1 per cent dispersion is a mixture of 1 gm. of gelatine in 99 cc. of water. 



{All substances were examined at room temperature. 18 C. 



corresponding percentages of gelatine which have been established, 

 and these will serve as standards for the viscosity values of pro- 

 toplasm given in this paper. 



Just how accurate percentages of gelatine dispersions are going 

 to prove to be as standards of viscosity is somewhat doubtful, in 

 view of the sensitivity of gelatine to such influences as electrolytes, 

 length of period warmed (25, p. 121), etc., which greatly influence 

 its solidification temperature. The percentages of concentration 

 at which gelatine will set, as given in the literature, vary con- 

 siderably. Taylor states that a 10 per cent dispersion of gelatine 



5 Bacto-gelatine, "Difco" standardized, in granular form, with a moisture con- 

 tent less than 4 per cent, made by the Digestive Ferments Company of Detroit, and 

 sold by Arthur H. Thomas Company of Philadelphia. 





