152 J. F. MCCLENDOX. 



Sumner showed that as the fish becomes enfeebled by the ab- 

 normal medium, it becomes more permeable to salts. 1 Whether 

 the direct action of the abnormal medium, or the blocking of 

 the gill capillaries, produce the increase in permeability, has not 

 been experimentally tested. However, the gills themselves would 

 not be asphyxiated by blocking of their capillaries, and it seems 

 probable that the change in permeability is due to the direct 

 action of the medium. 



We may conclude therefore that the death of the fish results 

 from the osmotic exchange. This may be sufficient to cause death 

 while the fish still maintains its normal semi-permeability, or 

 death may occur only after increase in permeability, due to the 

 direct action of the medium on the osmotic membranes. 



A similar increase in permeability may explain Wo. Ostwald's 

 observations on fresh-water Gammarus in pure salt solutions. 2 He 

 found that the ratio of the rapidity of death to the concentration 

 is about constant up to a certain point, above which it is much 

 greater. This critical concentration has nothing to do with the 

 osmotic pressure, since it is different for different salts. Perhaps 

 at this concentration the salt made the membranes more per- 

 meable. 



Schiicking 3 found that nicotine and strychnine made the skin 

 of Aplysia more permeable to salts. Since cocain retarded 

 shrinkage in hypertonic solution, he supposed that the hydro- 

 static pressure produced by the muscles aided shrinkage. How- 

 ever the hydrostatic pressure is probably very small, and the 

 effect might have been due chiefly to an increase in permeability 

 to salts, produced by the cocain. 



3. Secretion of Lymph and Tissue Juice, 



Hober supposes the raising of the osmotic pressure by the kata- 

 bolism of the tissues, causes fluid to be drawn out of the blood- 

 vessels, and states that the lymph in the thoracic duct has a 

 greater osmotic pressure than the blood. 



Traube states that the surface tension of transudates and 



1 Cf. Greene, above. 



2 PJliiger's Arch., 1905, CVI., 568. 



* Arch. Anal. Physiol., Physiol. Abt.. 1902, 533. 



