F. F Blackman. 
190 
The naturally alkaline Tradescantia is very resistant to the 
strain of plasmolysis unless first treated with dilute acid. 
Coagulation by chemical agents. As confirmatory evidence of 
the dominance of proteids, Lepeschkin shows that organic substances 
like alcohol, aldehyde, chloral, act upon the typical protoplast in the 
same way as upon egg-albumin. The concentration of each of 
these substances required to produce complete coagulation of egg- 
albumen in ten minutes is practically the same as that required to 
coagulate the plasma-membrane in ten minutes. 
Further, alcohol lowers the temperature of coagulation of both 
egg-white and Tradescantia protoplast in a similar way, for which 
detailed temperatures are given in the paper. 
The presence of lipoids in the plasma-membrane. Like Overton, 
Czapek and others, Lepeschkin finds evidence that lipoids are 
present in the plasma-membrane, but he dissents from Overton’s 
view that such bodies form a continuous film on the surface of the 
plasma and are the only intermediaries in selective absorption. 
According to Lepeschkin, if lipoids are present in the plasma- 
membrane, then the presence of these active absorbers of narcotics 
should bring it about that less strong watery solutions of narcotics 
would be required to coagulate this membrane than to coagulate the 
simple proteid of white of egg. While the coagulation of the two 
media by alcohol or aldehydes was found to require similar concen¬ 
trations; for narcotics like ether only one-third, for chloroform one- 
eighth, and for thymol one-thirtieth of the concentration coagulating 
white of egg suffices to coagulate the plasma-membrane. It will be 
noticed too that the more soluble the narcotic is in lipoids in com¬ 
parison with water, the more abundantly it is taken up and the 
more effective it is on the plasma compared with pure proteid; 
ether is 4-5 times as soluble in oil as in water, chloroform 30, 
times and thymol more than 100 times). 
If the lipoids do not form a continuous film over the cell they 
might be present as an emulsion or loosely combined with the 
proteids of the plasma. The last is Lepeschkin’s view and such 
lecithin-protein complexes are certainly known. 1 Nathansohn 
started the hypothesis that the surface-layer might consist of a 
mosaic of lipoids and living protoplasm (proteid) independently 
responsible for the uptake of substances soluble in fats and in water 
' Handovsky & Wagner, Broch. Zeits. XXXI, 1911, p. 32, 
