470 LESLIE B. AREY 



(Grawitz, '02). Experimentation with diluting media at the 

 critical concentrations which first produce the cups from discs, 

 or which cause laking and crenation, makes it certain that there 

 is considerable variability in the responsiveness of individual cor- 

 puscles. Weidenreich ('02) further notes that there is a limited 

 variation in different individuals, and Lackschewitz ('92) and 

 Hamburger ('02) have compared the unequal resistance of the 

 corpuscles in certain of the lower animals. 



May it be that the blood of certain individuals contains nor- 

 mally excessive numbers of cup-shaped corpuscles? Is it pos- 

 sible that this explains why some of our most careful workers 

 have been led to describe this form as normal? 



The teachings of comparative histology do not support the 

 cup shape; but it may be objected that the loss of the nucleus 

 among mammals is in itself directly or indirectly responsible for 

 the assumption of the cup shape (cf. Rindfleisch, et al.). In 

 this connection might be mentioned Howell's ('00) statement 

 that biconcavity is a physical advantage because the absorbtive 

 surface is increased, and the conclusion of Rice ('14) that the 

 biconcave form is physically the 'best' since it is one having 

 less surface energy than any surface obtained from it by a small 

 deformation consistent with constant volume. 



It is conceivable that the action of hypotonic solutions in 

 swelling corpuscles assymetrically is associated with the loss of 

 the nucleus. Whether the side through which the nucleus is 

 expelled becomes more elastic (weakened) or less elastic (i.e., 

 like scar tissue) is, however, pure conjecture. 



E. SUMMARY 



The shape of the mammahan red blood corpuscle depends 

 largely on the osmotic pressure of the examining medium. In 

 solutions corresponding to ca. 0.9 per cent sodium chloride the 

 erythroplastid possesses a biconcave form. In progressively 

 less concentrated (hypotonic) solutions water is imbibed and 

 the corpuscles swell to thin-walled cups, thick-walled cups, 

 dimpled spheres, and finally lake formjng 'shadows.' In hyper- 

 tonic media crenation results. 



