590 



a definition which holds the field at the present day ^). None the less 

 it is recognised by physiological histologists that the osmotic properties 

 of cells furnish conclusive evidence of the existence of a superficial 

 film which plays the part of a semi-permeable membrane, having a 

 different chemical and physical nature from the bulk of the protoplasm. 



Along with that of all other cells of the animal body the de- 

 scription of the structure of the erythrocyte also underwent a com- 

 plete change. Up to the date of the papers which have been referred 

 to, it was universally described as a vesicle, composed of an external 

 envelope or membrane enclosing coloured fluid contents. The rejection 

 of the idea of cell-membranes in general led to the substitution for the 

 vesicular theory of erythrocyte structure of what is known as the 

 "stroma" theory, which was first formulated by Rollett-), and was 

 strenuously defended by him to the last. 



This theory supposes the existence of a porous framework to the 

 corpuscle, the so-called "stroma", the pores or meshes of which are 

 occupied by the haemoglobin, uniformly diffused through it. In the 

 latest development of the theory the corpuscle is regarded as con- 

 sisting of a hyaline stroma with a hsemoglobin-holding en do soma, 

 these two parts corresponding with those which had been denominated 

 oecoid and zooid by Brücke^); the haemoglobin being fixed in 

 some unknown manner in an amorphous condition and the electrolytes 

 of the corpuscle being confined to the stroma^). 



During some twenty or five and twenty years the stroma theory 

 was almost universally accepted'^) and was adopted in all text-books 

 of Histology; it is still upheld in the chief German text-books^). But 

 during the last fifteen years the progress of the study of osmotic phe- 

 nomena of cells in general and those of the blood-corpuscles in particular 

 — has led many physiological histologists to abandon the stroma theory 

 and to revert to the vesicular theory of erythrocyte structure. 



1) Verworn, Allgemeine Physiologie, 4. Aufl., 1903. 



2) Wiener Sitzungsber., Bd. 46, 1863, and Stricker's Handbuch der 

 Gewebelehre, Bd. 1, 1871. 



3) Ueber den Bau der rothen Blutkörperchen. Wiener Sitzungsber., 

 Bd. 56, 1867. 



4) BoLLETT, Pflüger's Archlv, Bd. 82, 1900, p. 199. 



5) Kollmann, in 1873, set forth reasons in favour of a membrane 

 but clung to the notion of a net-like stroma with which the haemoglobin 

 is in combination. Zeitschr. f. wissensch. Zool., Bd. 23. 



6) v. Ebner, in Koelliker's Handbuch der Gewebelehre. Bd. 3, 

 1902, p. 739. — Ph. Stöhr, Lehrbuch der Histologie, 1904, p. 114. 



