SHAPE OF MAMMALIAN RED BLOOD CORPUSCLE 465 



lives actually diminish (i.e., shrink) the diameter of the cor- 

 puscle. If this shrinkage were unequal at the thin center and 

 thick rim a disc might conceivably become a cup, as Jordan 

 maintains. Furthermore, if the reagent does not act on all sides 

 of a corpuscle simultaneously, is not a buckling of the more con- 

 tracted side on which the reagent first acts to be expected? 

 Indeed, the preexistence of biconcavities would favor this altera- 

 tion. It seems plausible that the delicatelj^ constructed erythro- 

 plastid is more easily subject to distortion, through the action 

 of reagents, than are ordinary tissue cells, for it is neither sup- 

 ported by contiguous cells nor by intercellular products. 



If this reasoning be sound the variable action of osmic acid 

 on drawn blood allows of another interpretation. When blood 

 enters a drop of fixative directly from a minute needle prick in 

 the finger the conditions for unequal fixation would appear to 

 be present (Lohner). Besides cups, numerous wedge-shaped 

 corpuscles are seen; according to the conception of uneven fixa- 

 tion such forms are easily explained. The presence of more 

 discs in blood that has first come into contact with air need not 

 be interpreted as due to a rapid change from the cup to the disc 

 with a subsequent fixation of the latter form; assuming that such 

 corpuscles have not been exposed to air sufficiently to induce 

 incipient crenation, which conceivably could affect the physical 

 condition of the corpuscular membrane (without, however, 

 necessitating a change in form) , the result is explainable on the 

 basis of a more even intermixing of blood and the added fixative. 



The following experiment of Lohner ('11) which I have often 

 corroborated is instructive from this viewpoint: 



Experiment 2.1.3. If a droplet of blood be drawn by capillarity be- 

 tween two cover slips, separated by a hair and fused at one point, discs 

 are observed. (Blood should occupy part of the capillary space only.) 

 If 1 per cent osmic acid be now drawn in cautiously from one side 

 only, the conditions for uneven fixation are present and many cups, 

 some wedge-shaped discs, discs, and distorted forms are seen. 



D. DISCUSSION 



Only certain aspects of the problem of a more or less general 

 nature will be considered here, critiques of individual results and 



