THE CYTOPLASM 31 



albumin and other substances, when coagulated by various reagents, 

 often show a structure closely similar to that of protoplasm as ob- 

 served in microscopical sections. Biitschli has made careful studies 

 of such coagulation-phenomena which show that coagulated or dried 

 albumin, starch-solutions, gelatin, gum arabic, and other substances 

 show a fine aveolar structure scarcely to be distinguished from that 

 which he believes to be the normal and typical structure of pro- 

 toplasm. Fischer ('94, '95) has made still more extensive tests of 

 solutions of albumin, peptone, and related substances, in various 

 degrees of concentration, fixed and stained by a great variety of the 

 reagents ordinarily used for the demonstration of cell-structures. The 

 result was to produce a marvellously close simulacrum of the appear- 

 ances observed in the cell, reticulated and fibrillar structures being 

 produced that often consist of rows of granules closely similar in 

 every respect to those described by Altmann and other students of 

 the cell. After impregnating pith with peptone-solution and then 

 hardening, sectioning, and staining, the cells may even contain a 

 central nucleus-like mass suspended in a network of anastomosing 

 threads that extend in every direction outward to the walls, and 

 give a remarkable likeness of a normal cell. 



These facts show how cautious we must be in judging the appear- 

 ances seen in preserved cells, and justify in some measure the hesita- 

 tion with which many existing accounts of cell-structure are received. 

 The evidence is nevertheless overwhelmingly strong, as I believe, 

 that not only the fibrillar and alveolar formations, but also the micro- 

 somes observed in cell-structures, are in part normal structures. This 

 evidence is derived partly from a study of the living cell, partly from 

 the regular and characteristic arrangement of the thread-work and 

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

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

 ming as well as many .later observers has clearly seen fibrillar struct- 

 ures in the living cells of cartilage, epithelium connective-tissue, 

 and some other animal cells (Fig. 9). Mikosch, alsti, has recently 

 described granular threads in living plant-cells. 



Almost equally conclusive is the beautifully regular arrangement 

 of the fibrillae in ciliated cells (Fig. 13, Engelmann), in muscle-fibres 

 and nerve fibres, and especially in the mitotic figure of dividing-cells 

 (Figs. 1 6, 24), where they are likewise more or less clearly visible 

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

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

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

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

 less clearly in a spiral mass to form the so-called Xcbcnkcni. In all 

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



