ALCOHOLS 85 



penetrate the protoplasts. This must of course occur in the case of 

 Penicilliunti &c., unless the alkaloids undergo extracellular digestion 

 and are absorbed as other substances. The permanence or non-permanence 

 of plasmolysis cannot be used as a test for absorption or non-absorption, 

 since sufficiently strong solutions to cause plasmolysis rapidly kill the cells. 

 After prolonged immersal in a per cent, solutions, the osmotic pressure 

 of the cell may be slightly higher than before, but this might easily be the 

 result of an attempt at accommodation by increasing the percentage 

 of soluble substances in the cell-sap, and affords no proof that the 

 3 per cent, solution diffuses slowly through the protoplasm. 



It has already been mentioned that plants such as Elodea, &c. with- 

 draw nitric acid from a solution of Veratrin nitrate in water, causing 

 the Veratrin to be precipitated. This is because the nitric acid is used 

 in metabolism, but apparently not the Veratrin. The precipitate is mostly 

 extracellular, but occasionally the cell-sap of cells of Elodea and Trianea 

 becomes cloudy after long immersal in a dilute solution, and the cloudiness 

 is due to minute particles resembling those formed in the external fluid. 

 These particles dissolve again in dilute nitric acid, and disappear for the 

 most part when the living cell is treated with dilute alcohol. Hence they 

 are presumably composed of Veratrin, and the latter must penetrate 

 the protoplast slowly in the form of Veratrin nitrate, although the very 

 fact that it may accumulate in the cell-sap shows that it is not retained 

 by the protoplasm. 



In no case does the permeability of the plasmatic membranes of cells 

 containing coloured cell-sap appear to be affected by dilute solutions 

 of Muscarin and Atropin, as long as they remain living. The escape of 

 the coloured sap is always a sign that the cell is fatally affected, and 

 is, in fact, usually a post-mortem phenomenon. Similarly in cells killed 

 by acids or alkalies, turgor is almost always maintained up to death, 

 and if the action is at all rapid, the cells are fixed in an uncontracted 

 condition. 



SECTION 36. Alcohols. 



Dutrochet x observed that dilute alcohol (^V f 3^) caused a temporary 

 retardation of streaming in Chara, followed by a subsequent acceleration 

 to above the normal velocity. Both ethyl- and methyl-alcohol produce 

 this result on Char a > Nitella, Elodea^ Vallisneria, and Trianea^ in con- 

 centrations of not more than i to 2 per cent, strength. If the alcohol 

 is gradually applied, the first retarding effect, which is the result of shock, 

 is not shown, and only the accelerating influence is manifested. 



Above this strength of solution a retarding influence is shown, which 



1. c., p. 72 ; cf. also Klemm, 1. c., p. 44. 



