SHAPE OF MAMMALIAN RED BLOOD CORPUSCLE 457 



adding a droplet of blood to a diluted serum obviously depends 

 on the relative amounts of each used. It is believed that the 

 percentages stated in the following paragraph are sufficiently 

 accurate for the purpose at hand. 



WTien a droplet of blood is mixed with human serum contain- 

 ing ca. 25 per cent water some erythroplastids assume the shal- 

 low cup shape shown in figure I, B; most, however, remain as 

 biconcave discs (A). When ca. 40 per cent water is present 

 there is a great preponderance of typical cups, with here and 

 there an unchanged disc. These cups appear somewhat like 

 figure 1, D in ca. 50 per cent mixtures. In dilutions containing 

 ca. 60 per cent water, the walls of the cups become swollen and 

 the concavity is reduced (E); this imbibition is so marked in 

 mixtures of ca. 65 per cent water that the appearance is that of 

 deeply dimpled spheroids (F). Perfect spheres result when the 

 water content of the mixture is ca. 70 per cent.^'- In concen- 

 trated serum erythroplastids crenate. 



It is evident, therefore, that the shape of a corpuscle is, at 

 least in part, a function of the concentration of the medium, 

 the changes being referable to the action of osmotic pressure. 

 In progressively hypotonic solutions the corpuscles imbibe in- 

 creasing amounts of water, ultimately becoming spheres and 

 laking. In hypertonic media, water is given up and crenation 

 results. All corpuscles, however, are not affected similarly by 

 the same concentration. This is strikingly shown by crenation 

 experiments and especially by dilution phenomena. When the 

 percentage of water present is 25, only part of the corpuscles are 

 clearly affected. Such a result might conceivably be due to the 

 unequal elasticities of the corpuscular membranes which oppose 

 differently imbibitory swelling. 



Analogous series were obtained by diluting Tyrode's solution 

 and 0.85 per cent saline with distilled water. The shapes of the 

 red corpuscles at the various dilutions approximated closely 



'^ The following measurements hold: 



Diameter of disc 7.5 

 Diameter of cup 7.0=1= 

 Diameter of sphere 5.0 



