16 GENERAL BIOLOGY 



instead of a gas and liquid (as in soapsuds), we have 

 two liquids of different densities and qualities, form- 

 ing what is known as a diphasic system. According 

 to Biitschli protoplasm is such an emulsion, com- 

 posed on the one hand of substances insoluble in 

 water which are highly viscous or sticky, and on the 

 other hand of a watery medium supporting the 

 various-sized particles of the former. 



Owing to the fact that the refractive indices of 

 the different components of protoplasm are nearly 

 the same, it is very difficult to see its structure in 

 the unaltered living state. Biologists have recourse, 

 therefore, to " fixing " or coagulating the protoplasm 

 with various poisons and dyeing it with aniline or 

 other colors. Under such circumstances protoplasm 

 appears to have a skein or net structure. But this 

 has been interpreted as being merely the appearance 

 of particles caught and held by surface tension 

 the films of the bubbles, so to speak, which when 

 set and viewed in connection with those of adjacent 

 bubbles appear to form a continuous layer or thread. 

 This view is justified by the fact that artificial emul- 

 sions, subjected to the same processes of fixation 

 and staining employed in the study of protoplasm, 

 show a strikingly similar appearance to that of 

 living substance. More recent investigations, in- 

 volving the dissection of living protoplasm under 

 the highest powers of the microscope, seem to point 

 to the conclusion that Biitschli's conception may 

 require certain modification. The physical " phases " 

 in which protoplasm consists appear to be all col- 



