208 PROTOPLASM 



the framework and its contents, and I can only, as before, 

 assert in the most definite manner that in the thinnest 

 sections, or with the intensest staining, I could never obtain 

 any coloration whatever of the contents of the meshes or 

 intervening matrix. As I have remarked before, the in- 

 vestigation of thicker sections, or even of whole layers 

 of protoplasm, as was the method of Schwarz in all cases, 

 proves nothing at all in this respect ; for even if only a few 

 layers of alveoli were superposed upon one another, it must 

 naturally give an appearance as if the intervening substance 

 also possessed a fainter colour, because both above and below 

 a mesh which is exactly in focus there lies a quantity of 

 coloured matter which affects the light transmitted. Exactly 

 the same holds good, in my opinion, for the reticular 

 precipitates prepared artificially by Schwarz, for which also 

 he assumes a homogeneous or granulated ground substance 

 composed of the same material. If Schwarz saw precipita- 

 tion films, which were originally homogeneous, becoming 

 afterwards granular and reticular, I assume, until further 

 light has been thrown on the subject, that it was nothing 

 to do in this case with structures which became formed 

 within the homogeneous film, but it was a matter of deposits 

 that appeared subsequently in the form of granules, networks, 

 and crystals. 



I will not follow up this subject further, since as yet I 

 have but few observations at my command upon reticular 

 precipitates and coagulations. Yet I agree completely with 

 Schwarz that coagulated drops of white of egg, as also a 

 precipitate of ferrocyanide of iron (from rather concentrated 

 solutions), appear very finely reticular, and possess great 

 resemblance to protoplasmic structures. In the case of a 

 precipitate of Prussian blue, it can scarcely be doubted that it 

 is only the result of a serial arrangement of minute stained 

 granules, and the same will also probably hold good for the 

 precipitates of colloidal bodies. 1 With regard to this, and 

 also with reference to protoplasmic structures generally, it 

 seemed to me of importance to test in what way very 



1 Upon this point see the Appendix at the end of this chapter (pp. 216- 

 219 infra) for the changed opinions which I now hold. 



