TENSION PHENOMI \A OF LIVING I LI-MI. NTS. 



Ovrrton observed that if the cloaca and mouth of a frog in 

 ire-h water are closed, the frog constantly increases in weight. 

 This can be prevented by the addition of .7 per cent. XaCl to 

 the medium. In a hypotonic solution water is constantly ab- 

 s<>rbed by the skin and excreted by the kidney-. Fischer's 1 

 experiment, in which ligature of the leg of i frog caused great 

 i low the ligature is probably to be explained 1>\ the 

 f.n i tin; v. ater was absorbed by the skin but could not reach the 

 kidne\~. -jure the blood circulation was stopped. In regard to 

 Fi-cher 1 - t \pl. mation, compare the results of Sidbury and < , ; 

 Sunmi i i .in. Inded that in the fish, the gills are the chief -eat of 

 \ch.uige. 



It appear-, therefore, that osmosis occurs through tin iiiu-ii 

 mi-Hi unhiding gills), kidneys and gut simultaneously, and since 







the contents of the gut and kidney tubules are not the -a me a- the 

 medium, u -hould not expect an osmotic equilibrium bet \\eui 

 the body tluids and the medium. Furthermore, all three . if these 

 membrane- m.i\- show irreciprocal permeability. 



I n -li-\\.iter li-li and non-migratory marine fish an- killed b\ 

 ii changes in the medium, even though it be \<r\ ^r.nlual. 



I'.ert m. tiiii. lined that if fresh-water fish are placed in sea \\.iter. 

 ilie ^ill i .ipill.u ies contract and become blocked b\ the distorted 

 i "i 'liii-t le-. lii naked-skinned fishes, not only the v;ills are 

 .itterted. but \\.iter ma\' be lost from the tissues. 



lien .UK! Simmer both agree that the salts in sea water cannot 

 IM replaced 1 .\ anv other substance, without can-in- tin- death 

 oi certain marine fishes. Mosso 3 claimed that \\hen -hark- are 

 placed in tn-li \\.uer, the gill capillaries become ><> 1 ilocke< 1 \\ith 

 laked corpu-cles that physiological salt solution coiuM ni be 

 1 1 -reed tlimu^h ilu-m. He observed that the difference- in the 

 resistance of ctiiain tish to changes in the -alt cmuent of the 

 medium, i-oi-re-]ioiided to differences in the iv-i-tance of their 

 bl..id it 11- to the luemolytic action of such changes. Simmer. 1 

 ho\\e\er. -late- that this blocking of gill capillarie- doe- ma 

 occur in -hark- or marine teleosts in fiv-h water. 



1 Fischer, M. H., d -l.-nia," J. NViloy & Sons, i<. 

 x Exper. /';<>. and Mfdicine, 1911. \'II., m.j. 



/. (,///'.. isyo. N.. 570. 

 4 /'- s >-nth Inttrnat. Zoo/. Congress, Bost"n, 



