140 PROTOPLASM 



through the lining and the epithelium cells), for which 

 opportunity is often given by longitudinal sections of the 

 animal, the following peculiar structure can be seen (Plate 

 XII. Fig. 3). The lining consists of rather thick and 

 darkly stained rounded or oval bodies, which vary to some 

 extent in diameter. These bodies have a distinct mesh work 

 structure, and carry numerous strongly stained granules in 

 their nodal points. They appear connected with one 

 another by a paler, less strongly stained meshwork, which, 

 however, also carries scattered granules in its nodes. After 

 this composition has been made out in tangential sections, 

 it is also possible to observe a corresponding state of things 

 in longitudinal sections through the cuticular border. The 

 more strongly stained portions appear in longitudinal section 

 as conical bodies, which are united by a paler intervening 

 alveolar meshwork. Since these conical bodies, which are 

 pointed towards the inner surface of the lining, are not quite 

 of equal length and thickness, they appear to differ somewhat 

 in size in a tangential section, as the figure shows. 



O ' O 



8. Liver Cells of Rana esculenta and Lepus cuniculus 



Since liver cells have been made use of so often for 

 studies on the structural relations of the protoplasm, I 

 investigated them in the thinnest possible sections. The 

 pieces of liver in question were hardened in the picro- 

 sulphuric-osmic acid mixture, and then stained with iron- 

 hsematoxylin in the manner described. The thickness of the 

 finest sections must certainly have been under 1 //,, and 

 therefore, in any case, would not have been above the 

 medium thickness of a mesh of the protoplasmic frame- 

 work. 



Sections prepared in such a way through the frog's liver, 

 and, for the most part, stained still further on the slide 

 with iron-hsematoxylin or vesuvin, show at once a very 

 beautiful net-like protoplasmic framework in the clearest 

 and most convincing manner, of which Plate VII. Fig. 1, 

 and also Photograph VIII., give a representation. I 

 expressly point out that the figure was drawn with all 



