132 GEORGE G. SCOTT. 



in through the gill membranes. But what of the constant effect 

 of this excessive work on the kidneys in the case of specimens 

 successfully transferred from sea water to fresh and living for a 

 number of years in fresh water, as Smith has described. Such a 

 view is manifestly weak. There is but little doubt that the 

 changes brought about in the organism due to immersion in 

 fresh water are due to diffusion of water through the gill mem- 

 branes, and that the permeability of the gill membranes is changed. 

 A second view as to what subsequently happens is that the gill 

 membranes after this attack are modified. And in such a 

 process must not other parts of the organism be concerned? 

 The gill membranes cannot be changed of themselves. They 

 are under the influence of the nervous system. Blood carries 

 materials to the membranes. The experiments show analogies 

 to the response of animals to the inoculation of bacteria, a period 

 of ups and downs, recovery in the case of some, death in others. 

 It seems to me that views which place the emphasis upon the 

 influence of the external agents on the membranes and explain 

 acquired impermeability as being due to some sort of tanning 

 action, are incomplete. What kind of respiration could take 

 place through tanned membranes? Evidence has been obtained 

 from the plant world to the effect that plant cells can modify 

 their permeability. It is not necessary, however, to agree with 

 Philip, '10, when he says, "This fact and others which have just 

 been quoted, will serve to show that a purely physical theory 

 of the exchanges which take place across a living membrane is 

 inadequate; there is a physiological permeability as well as a 

 physical permeability." This is but begging the question. 



LITERATURE LIST. 

 Bert, P. 



'71 Sur les phenomenes et les causes de la mort des animaux d'eau douce que 



Ton plonge dans 1'eau de mer. Comptes rendus de 1'acad. des sciences, 



1871, t. LXXIII. 

 Garrey, W. E. 



'05 Osmotic Pressure of Sea Water and of Blood of Marine Animals. Biol. 



Bulletin, Vol. VIII., p. 257, 1905. 

 Loeb, J. 



'oo On lon-proteid Compounds and their Role in Mechanics of Life Phenomena. 



i Poisonous Character of a Pure NaCl Solution. Am. J. Physiology, Vol. 



3, No. VII., p. 327, 1900. 



