44 



GENERAL SKETCH OF THE CELL 



microsomes in certain cases. In many Protozoa, for example, a fine 

 alveolar structure may be seen in the living jirotoplasm ; and Flem- 

 ming as well as manv later observers has clearly seen fibrillar struc- 

 tures in the living cells of cartilage, epithelium connective-tissue, and 

 some other animal cells ( Fig. 9). Mikosch, also, has recently described 

 ^;v7;///A7/' threads in living plant-cells. 



Almost equally conclusive is the beautifully regular arrangement 

 of the fibrillct' in ciliated cells ( Fig. 17, Fngelmann), in muscle-fibres 

 and ncrve-hbres, and especially in the mitotic figure of dividing cells 





B 







C 



D 



Fig. 18. — Cells of the pancreas in Amphibia. [Mathfavs.] 



A-C. Nectiiriis ; D. Rami. A and H represent two stages of the " loaded " cell, showing 

 zymogen-granules in the-peripheral and fibrillar structures in tlie basal part of the cell. C shows 

 cells after discharge of the granule-material and invasion of the entire cell by fibrillie. In D por- 

 tions of the fibrillar material are coiled to form the mitosome (" paranucleus " or " Nebenkern "}. 



(Figs. 2 1, 31), where they are likewise more or less clearly visible 

 in life. A very convincing case is afforded by the pancreas-cells 

 of Nccturiis, which Mathews has carefully studied in my laboratory. 

 Here the thread-work consists of long, conspicuous, defmite fibrillae, 

 some of which may under certain conditions be wound up more or 

 less closely in a spiral mass to form the so-called Nebcjikern. In all 

 these cases it is impossible to regard the thread-work as an accidental 

 coagulation-product. In the case of echinoderm eggs, I have made 

 ('99) a critical comparison of the living structure, as seen under powers 



