1893.] Secretion in the Skin of the Common Eel. 39 



Fibrdblasts. Among the cells of the lower layers of the epidermis 

 are found small cells 4 to 5 ^ in diameter resembling lymphocytes, 

 generally in little masses, and with nuclei often presenting mitotic 

 figures. Such cells have been described by Langerhans in Petromyzon 

 Planeri, List in Cobitis, and Fritsch in Malapterurus. List has 

 described them as wandering cells passing in from the corium, and 

 considers that they are finally extruded in degenerated form, as 

 Stohr has demonstrated in the case of the tonsil. .Fritsch saw no 

 evidence of this extra-epidermic origin in Malapterurus, and came to 

 the conclusion that these cells supply the surface epidermic scales. 

 In the Eel these cells are undoubtedly in their origin foreign to the 

 epidermis, and can be traced from the blood vessels of the corium 

 through the basement membrane. In the epidermis itself all forms 

 can be traced between the lymphocyte-like cell (fibroblast) and con- 

 nective tissue cells with fine processes, which abound especially in the 

 lower layers. Leydig has already demonstrated that connective 

 tissue cells other than chromatophores may exist between the epider- 

 mic elements of Fish (Cyprinus carassius), and it is interesting to 

 note that Langerhans, who first described these " kleine B/undzellen," 

 was of opinion that they represented contracted chromatophore-like 

 cells devoid of pigment. It is easy to demonstrate a complete net- 

 work of connective tissue in the epidermis by sections parallel to the 

 surface, especially in cases where the bodies of the club cells have 

 become shrunken, and its function appears to be to hold together a 

 tissue which, on account of the peculiar processes involved in secre- 

 tion, would otherwise be of very labile nature. 



The process of secretion, therefore, so far as it can be deduced 

 from the appearances in the epidermis of slowly secreting winter 

 Eels, appears to be as follows : 



Goblet cells, the direct descendants of palisade cells, are gradually 

 forced to the surface by young epidermic cells derived from the 

 same source. On nearing the surface these swell, probably by imbibi- 

 tion of water, and, a stoma forming in the theca, the contents are 

 discharged, the remainder of the cell not necessarily being at once 

 extruded, but capable of undergoing regeneration. The club cells from 

 the same origin end in (i) a spirally wound fibre mass, which, after 

 probably helping, by a kind of " elater " action, to remove the surface, 

 is discharged and breaks up into the slime fibres ; and in (ii) a mass 

 of granular material inclosing the original nucleus, also discharged, 

 and giving rise to the granules and nuclei of the slime. 



Histology of Artificially Stimulated Epidermis. The details of the 

 secretory act deduced from the observation of the slowly acting 

 skins of winter Eels are confirmed, and in some points extended, by 

 the observation of stimulated skins. 



Chloroform vapour applied to the headless or intact animal causes 



