SOAPS, PROTEIN 1)1 1; I \ ATIVES AND TISSUES 247 



prove this point are subject to serious question, the observations 

 detailed in this volume l show how such occasional findings may 

 be explained. 



After the state described in B of Fig. 114 has been attained 

 it needs to be remembered that every salt water droplet is enclosed 

 within a hydrated colloid membrane. But these are now osmotic 

 systems; for the so-called semipermeable membranes of the physical 

 N/.S-, which allow water to pass through them but (as commonly 

 alleged) no dissolved substances, are also nothing but hydrated colloid 

 membranes. None of them are really impermeable to dissolved sub- 

 stances, but they allow the passage of such only very slowly. The 

 <ed -matous cell dehydrated from within may therefore swell still 

 more if water is given, for it has been converted into a series 

 of tiny osmotic systems, in other words droplets of concentrated 

 salt solution in semipermeable bags of hydrated colloid. 



These remarks must not, however, be misunderstood. The 

 normal cell is no such system and the play of osmotic forces within 

 it is practically zero. 



From their observations on oadema the clinicians have come 

 to the false conclusion that the way to treat it is to withhold 

 salt. What is necessary is to give salt but to withhold water. 



4 



We may now return to tin- general question of the possibilities 

 for the. development of osmotic properties by any cell under 

 physiological or pathological circumstances. 



Obviously, whenever the hydrated protein mass moves under 

 iti- influence of physiological activity or in consequence of 

 injury, etc., in the direction of increased hydra i ion and increased 

 solubility in water it moves also, in the direction of " increased 

 osmotic pressure," increased electrical conductivity, increased 

 fluidity and decree cosity; while changes in the direction 



of decreased hydration capacity and decreased solubility make 

 for an opposite set of cha i in.-, h is well to bear in mind t he simple 

 nature of these cha i in.-, lor in them is carried the "explanation " 

 of the, biological terms which to-day inijMMle progress in physiology 

 or pathology. 



'Srr ,, : ,nr 1 1 :j 



