PROTOPLASM. 8l 



tion of aniline blue in water, etc., is characteristic 

 of protein substances. 1 



For the preparation of aleuron-grains the fol- 

 lowing method is employed in the Copenhagen 

 laboratory : The sections are treated for several 

 days with a five per cent, alcoholic solution of 

 corrosive sublimate, according to Pfeffer's plan. 

 They are then colored by an aqueous solution of 

 eosin, and mounted for study in acetate of potas- 

 sium and water in equal parts. The crystalloids 

 are thus rendered very distinct ; and, if the eosin 

 solution has not been too concentrated, they com- 

 monly assume a red shade, different from that of 

 the ground mass. 



PROTOPLASM. 



Protoplasm is the living portion of the cell. 

 The chemical cause of this life if, indeed, such 

 chemical cause exist has not yet been discov- 

 ered ; but it appears as if some steps have been 

 taken toward the solution of this interesting prob- 

 lem. Quite recently a reaction for living proto- 

 plasm has been discovered. In this state it con- 

 tains free aldehyde, which does not exist in dead 

 protoplasm. This substance precipitates metallic 

 silver from even an extremely dilute alkaline solu- 



1 Cf. Vines : Chemical composition of aleuron-grains. Royal Society 

 of London, May i ?, 1880. Nature, 1880, vol. 22, No. 552, p. 91. Journ. 

 of the Royal Micr. Soc., 1880, Vol. III., p. 667. 



