THE CYTOPLASM 3 I 



albumin and other substances, when coagulated by various reagents, 

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

 serv^cd in microscopical sections. Bijtschli has made careful studies 

 of such coagulation-phenomena which show that coagulated or dried 

 albumin, starch-solutions, gelatin, gum arable, 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 sinudacruui 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 j^reserved 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, also, has recently 

 described granular threads in living plant-cells. 



Almost equally conclusive is the beautifully regular arrangement 

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

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

 (Figs. 16, 24), where they are likewise more or less clearly visible 

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

 of Nccturus, 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 Ncbenkcni. In all 

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



