STRUCTURE OF THE RED BLOOD CORPUSCLES. 409 



a 6). A retraction of the cell contents from the membrane 

 has here been considered to occur, and we may associate with 

 this the forms which Kemak* and more recently Preyerf 

 have described in regard to the fission of blood corpuscles, in 

 which a gradually deepening furrow detaches a coloured por- 

 tion of the blood corpuscle, whilst a glass-clear substance (the 

 empty membrane) becomes apparent between the separating 

 part and the investing contour line of the rest of the corpuscle. 

 Hensen,J who has devoted considerable attention to the first- 

 mentioned forms, sought to explain the retraction of the con- 

 tents from the membrane, the existence of which he believed, 

 from his observations of these forms, to be proved, by ascribing a 

 protoplasm to the red blood corpuscles, which invests the nucleus 

 and lines the inner surface of the membrane (primordial 

 utricle), these two portions being connected by delicate radially 

 coursing fibres, in the spaces of which the closed cell fluid is 

 ocontained ; he supported this view especially upon the existenc 

 of colourless fibres running in a radial direction from the 

 nucleus, and it is well known that similar observations have 

 been made by other histologists. But, independently of these 

 fibres, which certainly do not represent any constant structure 

 in the blood corpuscles, since they only appear to be met with 

 under exceptionally favourable circumstances, the protoplasm 

 distributed throughout the whole corpuscle must, according 

 to the view of Hensen, form a considerable portion of their 

 substance. The term protoplasm is now frequently so em- 

 ployed as to render it very desirable that its application 

 should be restricted to a definite idea ; but if we pay attention 

 to the appearance and the most striking peculiarities of the 

 protoplasmic masses described by Max Schultze and by 

 Kiihne ; || and if also, as will be subsequently discussed, we 

 consider that in their development the red blood corpuscles are 

 formed at the expense of the cells composed of contractile 



" Miiller's Archiv, 1858, p. 178, Taf. viii. 



t Virchow's Archiv, Bandxxx., p. 417, Taf. xv., figs. 26 and 27. 

 J Zeitschrift fur wissenschaftliche Zoologie, Band xi., p. 260, etc. 

 Das Protoplasma der Rhizopoden uud der Pflanzenzellen. Leipzig, 1863. 

 || Untersuchungen uber das Protoplasma und die Contractilitdt. Leipzig, 

 1864. 



