80 



SOLUTIONS AND PROTOPLASM 



[Cn. Ill 



fishes the eyes are forced out, the foot of gastropods swells, the 

 blood corpuscles swell up and burst, and muscular tissue may 

 increase as much as 6 times in volume. The enlargement of 

 the different tissues is exhibited in the following table, which 

 shows the percentage increase in weight and volume of organs 

 of Scyllium canicula, placed in fresh water. 



All of these phenomena are clearly explicable upon the assump- 

 tion of their production by endosmosis. 



c. The pressure due to dense solutions may become very 

 great, amounting, as I have said, to many atmospheres. So it 

 is not surprising that a change of medium may rend cells or 

 at any rate kill organisms. This result may be brought about 

 either when the denser solution is inside of the body or outside ; 

 the former case is realized when marine animals are plunged 

 into fresh water, the latter when fresh-water animals are 

 plunged into solutions of salts. Studies upon the fatal effects 

 of varying the concentration of solutions have been made by 

 BERT ('66), PLATEAU (71), COUTANCE ('83), RINGER and 

 BUXTON ('85), DE VARIGNY ('88), MASSART ('89), GOGORZA 

 ('91), and RICHTER ('92). 



BERT'S ('66) studies were made upon marine fish which he 

 plunged into fresh water. In a vessel holding 4.8 litres of 

 fresh water, a mullet died in 44 minutes, and a Sparus in 86 

 minutes. Since the fishes lived longer in a sugar solution, 

 BERT concluded that death was due to diminished density of 

 the medium. In this conclusion he was nearer the truth than 

 his immediate followers in this work. 



PLATEAU'S ('71) observations were made upon all classes of 

 Invertebrates, but especially upon Arthropods. He subjected 



