SHAPE OF MAMMALIAN RED BLOOD CORPUSCLE 459 



Experiment l.G.l. A drop of human blood, diluted in human serum, 

 on examination showed the erythroplastids to be typical discs. When 

 a droplet was transferred to a hanging drop, composed of half serum 

 and half water, the corpuscles assumed cup shapes (fig. 1, -S). The 

 disc shape was recovered by retransferring to normal serum but in 

 the 50 per cent serum-mixture swollen cups (like fig. 1, F) were again 

 obtained. Following a return to discs in normal serum, crenation was 

 effected by transference to somewhat concentrated (evaporated) 

 serum. 



Experiment 1.6.2. Disc-shaped corpuscles in normal serum cre- 

 nated in hypertonic serum. Transference to serum diluted one-half 

 with distilled water induced a return to discs for some corpuscles and 

 to cups for others. In hypertonic serum crenation again occurred. 



As the size of the droplet used in the transfer affects greatly 

 the ultimate concentration of the mixture, the figures given in 

 these experiments have no quantitative value. Considerable 

 variability was found in the responses of individual corpuscles. 

 It is perhaps significant that in experiment 1.6.1 the second 

 transfer to dilute serum produced more highly swollen cups 

 (fig. 1, F) than did the first transfer (fig. 1, -B) ; that it is indica- 

 tive of an increased elasticity of the corpuscular membrane 

 through injury is not impossible. Corpuscles in which crena- 

 tion has proceeded too far seem to be permanently injured and 

 incapable of a return to the normal; similarly figure 1, F, marks 

 the approximate stage beyond which corpuscles become irre- 

 versibly altered. In terms of saline solutions these limits cor- 

 respond to concentrations between 0.9 -f- per cent and 0.3=*= per 

 cent. The possibility of the action of a toxic time factor was 

 not investigated. 



The importance of these diverse dilution phenomena on the 

 question of the normal shape of the human erythroplastid seems 

 to me paramount. Since within wide limits the form of a cor- 

 puscle depends on the concentration of its medium, how can the 

 cup shape he normal when human serum must he diluted at least 

 one-third to produce this type? 



Experimentation with the serum of the cat and dog, both as 

 regards their own corpuscles and those of other individuals and 

 of man, has confirmed the conclusions already reached concern- 

 ing the normaUty of the biconcave disc. 



