Thirty fourth meeting. 



The Rockefeller iHstiUite for Medical Research. May 26, igog. 

 President Lee in the chair. 



59 (397) 



The comparative toxicity of sodium chloride and of 

 staining solutions upon the embryo of Fundulus. 



By ELIZABETH COOKE and LEO LOEB. 



\_From the Laboratory of Experimental Pathology of the University 

 of Pennsylvania ; and from the Marine Biological 

 Laboratory, Woods Hole.~\ 



What substances enter cells and upon what conditions the 

 entrance of various substances into cells and the permeability of 

 organized animal membranes generally depends, is as yet only very 

 imperfectly understood. The following experiments may not be 

 without interest in this connection. 



In studying the toxicity of stains upon star-fish eggs, we find 

 thionin, Bismarck brown, methylene blue and neutral red all to be 

 very poisonous, if the solutions are exposed to light. Among 

 these, neutral red is perhaps less poisonous than the other stains. 

 Solutions of eosin are very much less toxic than the other sub- 

 stances. Thionin, Bismarck brown, methylene blue and neutral 

 red easily penetrate into ova and stain them in a characteristic 

 way. Eosin does not stain living cells, but only enters in combi- 

 nation with the dead protoplasm. 



Very different is the degree of toxicity of these stains towards 

 the eggs of Fundulus. Here, Bismarck brown, thionin, methylene 

 blue and eosin are devoid or almost devoid of toxic action, whilst 

 neutral red alone possesses any marked degree of toxicity, if the 

 solution acts in the light. And the latter stain is likewise the only 

 one able to enter the healthy ova of Fundulus and to stain certain 

 parts of the embryo. We are therefore justified in the conclusion 

 that in the case of stains the toxicity of these substances towards 



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