591 



In its modern form this theory assumes the existence of a deli- 

 cate envelope with coloured fluid contents, with or without fine strands 

 stretching across the cavity of the flattened vesicle. It was formulated 

 in 1892 by the author in the following words : "The action of reagents 

 upon the human red blood-corpuscles shows that, although to all appear- 

 ance homogeneous, they in reality consist of an external envelope of 

 colourless material which forms a thin film enclosing the dissolved 

 colouring matter or haemoglobin. Thus when water reaches the 

 corpuscle, it passes through the film by osmosis and swells the cor- 

 puscle, causing it to become globular; eventually the film is burst 

 through, and the colouring matter escapes into the serum. Salt on 

 the other hand, by increasing the density of the fluid in which the 

 corpuscles float, causes a diffusion of water out of the corpuscle, and 

 a consequent shrinking and corrugation of the surface, the crenated 

 form being thereby produced. The separation of the haemoglobin from 

 the corpuscle can be eflected not only by water, but also by dilute 

 acids, by the action of heat (60^ C), the freezing and thawing of 

 blood, the vapour of chloroform, and the passage of electric shocks 

 through blood. The mixing of human blood with the blood or serum 

 of various animals also has a similar action, probably owing to differ- 

 ences of density or alkalinity. Tannic acid produces a peculiar effect: 

 the haemoglobin is discharged from the corpuscle, but is immediately 

 altered and precipitated, remaining adherent to the envelope in the 

 form of a round or irregular globule of a brownish tinge. 



Some of these reactions occur by process of osmosis as in the 

 case of water, but in others a physical or chemical solution of the 

 envelope of the corpuscles is produced and the haemoglobin is thus 

 allowed to escape. The envelope of the red corpuscle is often termed 

 the stroma (Bollett) but this name rests on an entirely false con- 

 ception of the structure of the corpuscle, and although of late years 

 almost universally used, it ought to be entirely abandoned. In adopting 

 the name, it was supposed that the corpuscle is formed of a homo- 

 geneous porous material (stroma), in the pores of which the haemo- 

 globin is contained, but there is no reasonable foundation for this 

 belief, whereas the supposition that there exists a delicate external 

 film or envelope enclosing a coloured fluid is in accordance with all 

 the known facts regarding the action of reagents upon these bodies" ^). 



In the following year this view was set forth in more detail, as 

 the following quotation will show (after describing the effect of adding 



1) E. A. Schäfer, Essentials of Histology, 3. Edit., 1892, p. 15—16. 



