Kalph W. Webster 23 



these laws, pass from the point of higher to that* of lower concentration of these sub- 

 stances and, of course, show a greater velocity the higher the temperature. A free 

 interchange of ions between the solution outside and that inside the sarcolemma is 

 naturally prevented by the relative permeability of sarcolemma as well as the varying 

 velocity of the ions in the two directions. As the rate of diffusion is dependent on 

 the density of the solution, the amount of fluid passing into a muscle from a hypertonic 

 solution would be much less than that entering from a hypotonic solution. Such is 

 the case as observed in our experiments, yet it is more than probable that osmotic 

 effects play a much greater rOle in these stronger and weaker solutions than in isosmotic 

 solutions where the ionic effects are more marked. 



Just how far the sarcolemma influences the process of diffusion cannot be stated, 

 inasmuch as our knowledge of the structure of this membrane is meager. The views 

 of Klein and van Beneden concerning the reticular structure of protoplasm are opposed 

 by those of Btitschli, who advances the theory of "foam-structure" of protoplasm. 

 Recent work by Hardy upon organic colloids and van Bemmelen upon inorganic 

 colloids show that the structures with which they were dealing in their experiments 

 were web-like structures in the interstitial spaces of which fluid is held by capillary 

 attraction, adsorption, and absorption. 



Briicke has advanced a theory of "pore diffusion" to explain the effect of an 

 animal membrane upon diffusion. He assumes capillary spaces in the membrane, 

 which spaces hold a layer of liquid by capillary attraction. If the space be very 

 small, then, of course, the membrane becomes relatively semi-permeable. Fick, in 

 addition to this idea of pore diffusion, assumes that this process occurs by a diffusion 

 through the molecular aggregates making up the membrane. This latter process is, 

 of course, dependent on laws of adsorption. 



We are, therefore, not in a position to say exactly what influence the sarcolemma 

 exerts upon the absorption noted in our experimelits, but we can state that a much 

 more complicated process is involved here than would be the case if the sarcolemma 

 were absolutely impermeable to the substances used. 



d. The element of time plays an important rOle in the phenomena observed in 

 our experiments. The effect during the first intervals is much more marked, relatively 

 speaking, than during the later ones and is also, in hypertonic solutions, of a different 

 phase. What do these variations denote? We might assume that the physiological 

 condition of the sarcolemma and of the muscle as a whole has been markedly affected 

 by the solution used. This assumption is borne out by Reid, who showed that the 

 passage of fluid through the skin of the frog is intimately connected with the physio- 

 logical condition of the tissue. He further showed that agents which tend to depress 

 the vital activity diminish the osmosis in the normal direction, while those agents 

 stimulating activity give rise to an increase in osmosis. It has also been shown by 

 Loeb, Lingle, Moore, and Kahlenberg and True that certain salts act as definite proto- 

 plasmic poisons. Loeb pointed out that pure solutions of NaCl, KCl, CaCl2 are poisonous 

 as far as contractile power of muscle is concerned. Miss Moore, in her work on trout 



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