244 COLLOIDS IN BIOLOGY AND MEDICINE 



tonic solutions of various alkali salts, and observed the order in which 

 they favored hemolysis. He established the following series: 



SO 4 < Cl < Br, NO 3 < I, and Li, Na < Cs < Rb < K. 



The anion series corresponds fairly well with the action of the anions 

 upon lecithin, so that we may safely assume that alkali salts may 

 bring about an increase or a diminution in the porosity of the plasma 

 pellicle. Other examples of this action on the part of neutral salts 

 are given in Chapter XXII (Salts). 



Substances which favor swelling in a diluted condition (p. 68) 

 may prevent it when they are more concentrated. It must also be 

 borne in mind, that besides hydrophile lecithin and albumin, hydro- 

 phobe cholesterin must also exist in the lipoid membrane. This lat- 

 ter is, however, precipitated by electrolytes, which cause the former 

 to swell. Thus there exists in the cell membrane a self -regulating 

 system, something like a compensation pendulum; when the tem- 

 perature rises, the center of gravity of the pendulum falls, but by a 

 combination of metallic rods the center of gravity is raised and 

 the fall is compensated. This compensatory action of hydrophile 

 and hydrophobe colloids appears to be an essential factor in the 

 automatic regulation of cell metabolism. 



The following considerations afford an explanation for some par- 

 ticular kinds of cells. R. HoBER* 3 properly calls attention to the 

 fact that, "the plasma film is really impermeable for everything 

 the cell needs or produces." It is impermeable for amino acids, 

 for the various kinds of sugar and soluble carbohydrates which are 

 formed in the interior of a cell from the undissolved carbohydrate 

 reserves and for inorganic salts and salts of organic acids. The in- 

 terchange of these substances, which naturally must occur, is on this 

 account, somewhat of a riddle. In my opinion, these phenomena 

 are less mysterious if we recall that with equal osmotic pressure 

 without and within, even the thinnest membranes interfere with 

 diffusion, as has been shown by H. BECHHOLD and J. ZIEGLER (see 

 p. 57). The most recent investigations of H. J. HAMBURGER on 

 blood corpuscles indicate that their transition membrane is not as 

 impermeable as was formerly believed. It will be understood thus 

 how the cells are sharply cut off in case of isotonicity, while if there 

 be hypertonicity, some substance may penetrate through the mem- 

 brane. This seems to me to be the meaning of the following ex- 

 periment of J. BANG*: if red blood corpuscles are placed in an 8 per 

 cent cane sugar solution and the solution is immediately diluted, 

 hemolysis occurs when the cane sugar concentration is 5.4 per cent. 

 If, however, the red blood corpuscles remain in the cane sugar solu- 



