508 
Seifriz.—Observations on the Reaction of 
It seems that there are two criticisms which can be directed against 
all theories of protoplasmic permeability so far advanced : first, their authors 
have attempted to explain a complex vital phenomenon on the basis of 
a single physical process ; and second, results obtained on one type of tissue 
are allowed to form the foundation of a theory intended to cover all living 
systems. 
Summary. 
1. Ethyl alcohol of a concentration of io per cent, will kill the cells in 
the average leaf of Elodea at the following rate: o-i per cent, of the total 
number are killed in 15 minutes, 1 per cent, in 20 minutes, 60 per cent, in 
30 minutes, 80 per cent, in 1 hour, 95 per cent, in 2 hours. 
2. The average cell of the leaf of Elodea is killed in the following con¬ 
centrations of ethyl alcohol in the following respective lengths of time: 
10 per cent, alcohol in 28 minutes, 9 per cent, in 2 hours, 8 per cent, in 
12 hours, 7 per cent, in 18 hours, 6 per cent, in 26 hours, 5 per cent, in 
40 hours, 4 per cent, in 3 days, 3 per cent, in 5 days, 2 per cent, in 10 days. 
3. Short treatment of the Elodea leaf cell in ethyl alcohol results in 
a reduction of osmotic pressure within the cell due, apparently, to an 
increase in permeability and consequent exosmosis of the cell contents. 
With longer treatment the osmotic value of the cell rises until it far 
surpasses the value of the untreated cell. 
4. Treatment in ethyl alcohol causes a pronounced stimulation to 
streaming in the Elodea leaf cell. 
5. The permeability of the Elodea leaf cell is increased and the osmotic 
value, therefore, decreased by brief treatment in a 1 per cent, solution of the 
glucosides, saponin, smilacin, and senegin. Longer treatment results in 
an increase of osmotic pressure. 
6. A change in the critical plasmolytic concentration of the salt 
employed for determining the osmotic pressure of a cell may mean either an 
increase or a decrease in permeability depending upon the interpretation. 
It was possible to show by several different observations that a loiver 
critical plasmolytic concentration means increased permeability in the case 
of saponin-treated cells. 
7. The saponins greatly stimulate the streaming of protoplasm. 
8. The theories of Overton, Traube, Czapek, and Warburg, bearing on 
permeability and narcosis, are considered, and it is shown that each theory 
is supported by experimental evidence, but none of them are alone sufficient 
as a complete explanation of all permeability phenomena. 
The experimental work on which this article is based was carried out 
in the laboratories of the Botanical Institute of the University of Geneva, 
Switzerland, where I enjoyed the privileges of a guest through the courtesy 
