130 PROTOPLASM 



Reticular structures, such as are described above, I find best 

 described by Pfitzner (1883), especially when the figures pub- 

 lished by him in 1886 are brought into comparison. The 

 radiating fibre-like structure was also then partially indicated. 

 The cell membrane mentioned by Pfitzner corresponds to the 

 pellicula. The threads of the network, according to him, sink 

 into this skin, and this, as a matter of fact, they do. 



After I had commenced my investigations in June 1890, and 

 had already reported briefly upon the presence of a marginal 

 layer of alveoli (1890, 1892), there appeared a communication 

 of Auerbach which agreed in many points with my statements. 

 Auerbach had also observed the alveolar layer, but had not seen 

 its radial striation. He interprets it as a cell membrane. It is 

 interesting that in double staining with eosin and aniline blue it 

 becomes coloured blue, while the protoplasm bordering on it 

 stains red. Auerbach furthermore noticed the cavity in the blood 

 corpuscle, but regarded it as a colourless and structureless 

 protoplasm, which he terms medullary substance, in contradis- 

 tinction to that which I regard as the sole protoplasm, which 

 is termed by him cortical substance. The reticular structure of 

 the protoplasm, which he observed after treatment with picric 

 acid, he looks upon as an artificial product, as a vacuolisation, in 

 fact, from which it seems to him a little strange that his medul- 

 lary substance, which is at all events much richer in water, 

 shows no such vacuolisation. All my experiences with regard 

 to the fixation with picro-sulphuric acid (I did not use pure picric 

 acid) of distinctly structured living protoplasm, speak against this 

 explanation of the net-like structure. Apart from many other 

 differences, my observations also contrast essentially with those 

 of Auerbach in regard to the distribution of the protoplasm, or 

 cortical layer, as he terms it. This he describes as spreading out 

 under the whole surface of the corpuscle as a layer of even thick- 

 ness, as is evident from an optical longitudinal section figured by 

 him. This section must, however, have been taken from a de- 

 formed corpuscle, since it does not represent its true shape, and 

 shows the nucleus separated by a thick layer of the so-called 

 cortical substance from the marginal layer of alveoli on each 

 side, a disposition which directly contradicts what I have 

 observed. 



Although I have not made this subject a matter of special 

 study, I would nevertheless state my belief that the central 

 hollow of the blood corpuscles is in reality a cavity contain- 

 ing cell sap, which, moreover, as has already been pointed 

 out above, is probably traversed by delicate strands of proto- 



