BLOOD, RESPIRATION, CIRCULATION AND DISTURBANCES 305 



lecithin and cholesterin in relation to water and salt solution are 

 entirely uninvestigated. Investigation of the swelling capacities of 

 such mixtures would greatly advance our knowledge of plasma 

 membranes. 



It is evident that the lipoids can form only very thin surface pel- 

 licles if we consider how small, in view of the analysis on page 304, 

 is the amount of cholesterin and lecithin they contain. 



A question remains: Is the membrane of uniform composition 

 and consistence? Against this view is the fact that on shrink- 

 ing, thorn-apple forms appear. This shape might also occur if 

 there were an inner framework, the interstices of which are filled 

 at the periphery with compressible elements. Such a theory best 

 fits in with physico-chemical observations. The pellicle of red blood 

 corpuscles is permeable for water, fat-soluble substances and to a 

 certain extent for cations and anions of the salts occurring in the 

 body. 



The existence of a fatty pellicle does not eliminate the probability 

 that the blood corpuscles may also form a fatty layer at an injured 

 point, which impedes the exit of hemoglobin (see p. 243). GRUNS* 

 discovered that red blood corpuscles could be cut up without the 

 subsequent exit of hemoglobin, and E. ALBRECHT * showed that blood 

 corpuscles divided by crushing or by gentle heating, to a certain 

 extent resumed their spherical form by reason of surface tension, and 

 retained their coloring matter. It must be borne in mind that red 

 blood corpuscles contain only 591 parts water to 316 parts hemo- 

 globin. If the hemoglobin were to appropriate all the water, which 

 is certainly not the case, we should obtain only a very viscous mass, 1 

 which would require a considerable time to swell or undergo other 

 changes, thus giving an opportunity for the formation of a surface 

 membrane (see p. 35). 



Based on my own hitherto unpublished studies on hemolysis and 

 on those of others accessible to me, I have formulated the following 

 hypothesis for the structure of red blood cells: they possess a sponge- 

 like framework consisting of a fibrinous mass, the stroma (to what 

 extent lipoids are involved in this framework is an open question 

 entirely immaterial to our discussion). The sponge is entirely 

 soaked with a salt-containing albumin solution, chiefly hemoglobin, 

 and has a very thin lipoid pellicle as a capsule. On the basis of 

 such a structure all the known properties of red blood cells find an 

 unstrained explanation. They would swell and burst in hypotonic 

 solution and shrink in hypertonic solution. Such salt solutions as 



1 It is easy to convince oneself of this by observing a pure suspension of 

 blood corpuscles becomes hemolyzed by a drop of arachnolysin. 



