GENERAL PROPERTIES: THE CORPUSCLES. 419 



of the red corpuscle is not completely known. It is usiuilly stated 

 that the corpuscle is composed of two substances, stroma and hem- 

 oglobin, together with a certain amount of water and salts and 

 also a certain amount of lecithin and cholesterin. The stroma is a 

 delicate, extensible, colorless substance that gives shape to the 

 corpuscles; it forms a mesh work or spongy mass in which the 

 hemoglobin is deposited. This latter substance forms the chief 

 constituent of the corpuscle, since it makes about 32 per cent, of the 

 weight of the normal corpuscle, and when dry from 90 to 95 per 

 cent, of the total solid material. According to another view the 

 corpuscles are vesicles with an external envelope or pellicle in 

 which lecithin and cholesterin are found, while the hemoglobin is 

 contained within.* Whichever view may be correct, great interest 

 attaches to the presence of the lecithin and cholesterin, whether 

 these substances are found in an external membrane or in a stroma 

 permeating the corpuscle. According to Pascucci the lecithin and 

 cholesterin constitute as much as 30 per cent, of the dry weight oi 

 the stroma, that is, of the portion of the corpuscle left after re- 

 moval of the hemoglobin. Such a large proportion of these two 

 substances is not found elsewhere in the body except in the myelin 

 sheath of the nerve fibers. It is believed that they play an impor- 

 tant role in maintaining the integrity of the corpuscles and 

 particularly in givmg to the peripheral layer or membrane sur- 

 rounding the corpuscles certain characteristic properties of 

 permeability. Under normal conditions this external layer 

 is easily permeable to water and to certain substances in solution, 

 such as urea, alcohol, and ether, but it is said to be impermeable 

 to the neutral salts; the concentration of sodmm chloride, for 

 example, is much greater in the plasma than in the red corpuscles. 

 The condition in which the hemoglobin exists within the cor- 

 puscle is not fully understood. It is evidently not in solution, 

 since the amount present is too great to be held in solution in 

 the corpuscle, and, moreover, even a thin layer of corpuscles 

 is far from being transparent. Nor is it deposited in the form 

 of crystals. It is assumed, therefore, that it is present in an 

 amorphous form. In various ways, however, the relations of the 

 hemoglobin within the corpuscle may be disturbed; so that it 

 escapes and enters into solution in the plasma. Blood in which 

 this has happened suffers a change in color, becoming a dark 

 crimson, and is, therefore, known as "laked blood." Laked blood 

 in thin layers is quite transparent compared with the normal 

 blood with its opaque corpuscles. 



* For recent discussions upon the histological structure of the corpuscles 

 see Weidenreich, "Anatom. Anzeiger," 1905, xxvii., and Schilling-Torgau, 

 "Folia Haematologica," Pt I, 1912, 14. 95. 



