390 PROFESSOR ARTHUR BOETTCHER. 



periphery of the blood corpuscles (fig. l\, c, e, i). In this case, 

 therefore, the whole blood-corpuscle is permeated by a network 

 of fine filaments. 



Lastly, there are blood-corpuscles in which the form of the 

 protoplasm shows itself, but indistinctly, and merely a darker 

 staining with carmine, and tl\€ somewhat granular nature of the 

 centre reveals the collection of protoplasm around the nucleus 

 (fig. 11,^). Such blood-corpuscles form the transition to the 

 perfectly homogeneous forms, in which carmine staining shows 

 nothing further than a faintly-coloured mass of uniform character, 

 in which the nucleus lies (fig. 11, /). In blood-corpuscles of 

 this sort, which are not stained, the outline of the nucleus is 

 usually indistinct, and on the surface there appears here and 

 there small dark spots, which may be dependent on remains of 

 the protoplasm still present (fig. 10, a). 



In the nucleus of the blood-corpuscles of the frog, after treat- 

 ment with an alcoholic solution of corrosive sublimate, the same 

 points can be observed as those already known from other obser- 

 vations. It possesses, as was already ascertained by Ranvier, a 

 sharply defined nucleolus ; but I have not by any means found 

 it present in all blood-corpuscles (compare figs. 10 and 11). The 

 nucleus is stained by eosine, but not at all, or only very faintly, 

 by carmine. 



Relying on the results of t/he above observations, I think I 

 may be permitted to oppose once more the current views on the 

 structure of the red blood-corpuscles. The doctrine of '' Stroma,'^ 

 originated by RoUet, generally accepted, and repeatedly com- 

 bated by me alone, is incompatible with the facts brought 

 forward. 



This so-called stroma is nothing more than a residue of the 

 colourless part of the red blood-corpuscles, varying much in form 

 and extent, which remains after the dissolution of the original 

 structural relations. The appearance and size of the colourless 

 residue depends upon the means which have been employed to 

 dissolve the blood- corpuscles, and upon the intensity with which 

 their action has taken place. Besides this, it is necessary to 

 take into consideration a point which has been entirely over- 

 looked, that the colourless part of the individual blood-corpuscles 

 appears to vary much in size. 



The stroma, as it has been displayed by methods hitherto in 

 use, is an artificial j^rorhict, and the ideas of the structure of the 

 red blood-corpuscles resting on it have rendered much more dif- 

 ficult the maintenance of a genetic relation between them and 

 the colourless blood-cor])uscles. The developmental connection 

 between red and colourless blood-corpuscles appears to be esta- 



