268 FINE-STRUCTURE OF PROTOPLASM II 



of ions, with its water of hydration, is responsible for the effect of 

 hydrating and dehydrating ions upon the properties of the erythro- 

 cytes. According to Fricke (1925), the electric properties of the wall 

 of the erythrocytes are such that the existence must be assumed of 

 a non-conductive layer 3 3 A thick. This thickness corresponds to the 

 lipidic part of the phosphatide layer I. Gorter and Grendel (1925) 

 assume that there is a bimolecular lipid film on the basis of the lipid 

 content of the erythrocytes; and this claim is likewise partly met. 



Finally, Winkler and Bungenberg de Jong calculate from the 

 stromatin and lipid contents of the erythrocytes of pigs (19.2, or 

 3.5 mg per ml of blood) that the orientated lipid molecules just cover 

 the surface of the blood corpuscles in the manner indicated (Fig. 133) 

 and that the layer of stromatin below is 1 20 A thick. From this we 

 get 1 50 A as the thickness of the total erythrocyte membfane (without 

 layer A) which, surprisingly, is of about the same order of magnitude 

 as the data obtained by Wolpers (1941) by means of electron optics. 

 However, this is only incidental, since Fig. 133 does not refer to the 

 dried, but to the hydrated envelope. 



Although this explanation of many interesting phenomena as- 

 sociated with the morphology and physiology of erythrocytes is un- 

 disputed, the model of Fig. 133 still raises a number of difficulties. 

 One of the first points to be noted is that analysis of the erythrocytes 

 has not revealed the presence of calcium. True, Winkler and 

 Bungenberg de Jong have calculated that the quantity of Ca present 

 is so small that it would escape detection in analysis, but they never- 

 theless consider it improbable that, given the percentage of calcium 

 in the blood serum, no Ca ions should be adsorbed on the erythrocyte 

 membrane. In the transition from the biconcave disc shape to the 

 globular, the surface must shrink by 37%. It is not clear how this 

 could take place without causing change of structure since, compared 

 to their normal distances, the molecules are already densely packed. 



An argument against the parallel radial orientation of all the 

 molecules is the slight optical anisotropy of the erythrocytes. Stro- 

 matin and haemoglobin can scarcely be said to represent chain mole- 

 cules; on the contrary, haemoglobin is known to be a globular 

 molecule. Should stromatin be filamentous, it would seem to me that 

 the orientation of those threads, c^iven their great length, is more 

 likely to be parallel to the surface than a radial one, as suggested. 



