TENSION PHENOMENA OF LIVING ELEMENTS. 149 



lowering the surface tension increased the absorption of NaCl 

 l>v the gut. 



Absorption is probably due to irreciprocal permeability of the 

 wall of the gut. Hamburger showed that dead gut and even 

 artificial membranes showed irreciprocal permeability to certain 

 substances. These artificial membranes were of different com- 

 position on their opposite surfaces (parchment paper-chrome 

 albumin or parchment paper-collodion) and he assumed that 

 tin \\all of the gut is composed of two osmotically different lavers. 

 In reality tin-re maybe more than two such layers, and the plasma 

 membrane- of the individual cells of the gut may show irreciprocal 

 permeability. 



TranU ' showed that the rate of absorption of a snlotance 

 by living v.ut is usually greater the more it lower- the Mir face 

 tension of water. The order of ions is: Cl >Br> I >N() 3 >SO I 

 Ill'<> : and K, Xa>Ca, Mg. The order of non-electrolytes, 

 . i' < online in Katzcnellcnbogen 2 is: glycocoll <urca<a( < t'>n< , 

 maun t <erythrite<glycerine<acetamid l methylalcohol, propyl- 



al< "h.il. am\ lalcohol. 



Tin- rati <>f absorption through dead ox gut according to i led in 3 

 \^:\'n \( i >C1>SO 4 and K > Rb> Na>Li >Mg ami m.mnit 

 <er\ thtiti < glycerine < urethan < glycocoll < amylenh\ draie 

 < gKtnl < urea < propylalcohol < isolnitylalcohol < methyl- 

 alcdlmi. ethylalcohol. 



Tin- action of poisons on absorption may be dm- in tin- alter- 

 atiiin i .t' tin plaMiia membranes of the individual celU. Ma\i-r- 

 hoi'< i and Mi in' state that even sugar in certain concentrations 

 inert -a-ed the permeability of the gut. 



2. ' ^niotic Relation of Aquatic Animals to the Medium. 



I redericq found that the salt content of tin- body fluids of 



marine in\ .Ttebrates is about the same as that of sea water. 



Henri and l.aloii 5 showed that the OMii"tic exchange bet \\eeii 



cirl(.m llu'nl of M-a urchins and holothunaii- and medium i- chielly 



/' \rch.. CXXXII. 



- /' ; . i Xl\'., 522. 



/' , . 1899, LXXX'III., 205. 



1 Hi,;li,-ni. /.fit.. 1910, XXX'II.. .^76. 

 1 NViiitri-t.-iii. 11. < .', 2. 



