18 SUMMARY OF CURRENT RESEARCHES RELATING TO 



skeleton of epidermal fibrils, which form a peripheral network at the 

 surface, and a series of internal fibrils running almost at right angles 

 to these ; (2) a substance wbich is apparently horn and which controls 

 the form of the cell ; (3) the cell-contents, apparently protoplasmic in 

 nature. The author strongly contests the current view that the horny 

 cells are dead, and believes that all layers of the epidermis — even the 

 outermost — are living. By suitable methods he has succeeded in de- 

 monstrating nuclei in horny cells. 



Fine Structure of Glandular Cells.* — Herr C. Golgi reports on 

 A. Negri's observation that in the pancreatic and parotid cells of the cat 

 it is possible, by means of Veratti's mixture (indirect method), to demon- 

 strate a complex network in the portion of the plasm facing the lumen 

 of the alveolus. The filaments anastomose and form a beautiful feltwork 

 which is not connected with the nucleus. Fine branches seem to be con- 

 nected with the efferent canals of the gland. 



Structure of Gastric Epithelium.f — Prof. Martin Heidenhain finds 

 that in the stomach of Triton tseniatus it is possible to study the first 

 origin of the mucus-plug of the epithelial cells. In the first stage the 

 cells show a striated margin composed of isolated protoplasmic rods 

 (Burstensaume). This peripheral " brush " increases in height, and 

 its elements secrete a connecting mucoid substance. Later on mucus is 

 secreted within the cell beneath this striated margin, the rods of the 

 margin being continued into the subjacent layer. They are there less 

 numerous, so that the superficial rods appear like the branches of can- 

 delabra. At a later stage the protoplasmic rods disappear, the basal 

 first, and the peripheral hist. Of the peripheral rods those at the sides 

 of the cell appear to persist, probably because they remain in connection 

 with the subjacent protoplasm. 



Classification of Epithelial Cells.! — P. Vignon discusses the varia- 

 tion in structure of the margin of epithelial cells, with special reference 

 to the so-called " motionless cilia " of insects and other invertebrates. 

 He suggests that epithelial cells generally should be arranged in three 

 categories : — (1) those with a united wall and with or without cuticle 

 or vibratile cilia ; (2) those with striated margin, whether cuticle or 

 cilia be present or absent ; (3) those with a margin made up of hollow 

 prisms, which, as before, may be ciliated or furnished with a cuticle. 

 The second group includes all cells in which the kinoplasm forms 

 trabecular, usually in the shape of cylindrical rods, placed perpendicu- 

 larly to the cell-margin. Such are the cells of the intestine and the 

 Malpighian tubes in the larva of Cldronomus, the intestinal cells of 

 Ascaris, and so on. The third group have been described in Amphioxus, 

 in Petromyzon, and in the larvae of Amphibians. Needless complications, 

 as the author believes, have been introduced by the failure to recognise 

 the fact that the cytoplasmic reticulum frequently tends to form tra- 

 becular. When cilia or peripheral striatum is present, these trabecular 

 have received special names, as " roots of cilia," &c, but they may exist 

 when there is neither striation nor cilia. Among the other questions 



* Verb. Auat. Ges., xiv. ; in Anat. Anzeig., xviii. (1900) Erg. Hft., pp. 17S-81. 

 t Anat. Anzeig., xviii. (1900) pp. 417-25 (4 figs.). 

 % Arch. Zool. Exper., viii. (1900) pp. 3-15 (7 figs.). 



