236 TEXT-BOOK OF PHYSIOLOGY. 



The stroma is elastic, and determines not only the shape of the corpuscle but 

 gives to it the properties of extensibility and retractility. 



The foregoing is the classic and generally accepted view as to the shape, 

 size, and structure of the red corpuscle. Nevertheless recent investigations 

 render it probable that the statements were based on observations of the 

 corpuscles under artificial rather than natural conditions, and therefore not 



strictly true. For many years 

 histologists from time to time 

 have stated that the red cor- 

 puscle is not circular and bi- 

 concave in shape, in the cir- 

 culating blood, but bell- 

 shaped, similar to that shown 

 in Fig. 99. It was not until 

 1902, after the publication of 

 Weidenreich's investigations 

 that this view began to receive 

 more attention than had 

 hitherto been accorded it. 

 c. d. Weidenreich preserved in a 



FIG. 99. THE SHAPE OF THE RED CORPUSCLE moist chamber a hanging drop 

 IN DIFFERENT MAMMALS. (Weidenreich.) a. Man. o f human blood, and on CX- 

 b. Dog. c. Pig. d. Rabbit. . ,. r 



animation found that the red 



corpuscles were bell-shaped though the depth of the bell cavity varied 

 considerably. An examination of the capillary circulation in the omentum 

 of the rabbit revealed the fact that the corpuscles in their natural medium 

 were also bell-shaped. The circular biconcave shape they ordinarily pre- 

 sent when a drop of blood is examined microscopically he attributes to cool- 

 ing, evaporation and concentration of the drawn blood. Experimentally 

 it was shown that when blood was added to 0.6 to 0.65 per cent, solution 

 of sodium chlorid all the corpuscles were bell shaped; but if the solution 

 was increased or decreased in strength, this form was at once changed. 



The dimensions of the bell-shaped cell according to Weidenreich are as 

 follows: 



Greatest diameter 7 microns o .007 mm. 



Diameter of cavity 3 microns o .003 mm. 



Height of bell 4 microns o .004 mm. 



Height of cavity 2.5 microns o .0025 mm. 



Thickness of wall at apex 2 microns o .002 mm. 



Thickness of wall at base 1.5 microns o .0015 mm. 



The foregoing observations have been confirmed by many subsequent 

 investigators. Thus Lewis states that if a drop of blood is placed immediately 

 on a warm slide and examined, the corpuscles exhibit the bell shape, but as 

 the slide cools they gradually become biconcave disks of the conventional 

 form. He also observed that the corpuscles in the capillary blood-vessels 

 of the omentum of the guinea-pig were bell-shaped and presenting an 

 appearance similar to that shown in Fig. 100. Radasch found on examina- 

 tion of fetal tissues such as the spleen, kidney, liver, placenta, etc., that the 

 great majority of the corpuscles in all situations presented the bell shape 

 rather than the circular biconcave shape. This observer is of the opinion 



