1893.] Secretion in the Skin of the Common Eel. 37 



Convinced that much of the variation in description of the appear- 

 ances of the secretory elements, and of the club cells in particular, 

 had arisen from the fact that no special care seems to have been 

 taken by any of the above observers to note the condition of the skin 

 as regards secretory activity at the time of fixation for histological 

 work, I have paid special attention to the condition of my fish, and 

 have also resorted to artificial methods of excitation. 



The Eel possesses both goblet cells and club cells in its epidermis, 

 and is therefore suitable for the study of the process of secretion in 

 both of these elements. 



To obtain skins in the lowest phase of secretory activity, hybern- 

 ating fish were obtained, rendered motionless by a successful trans- 

 fixion of the medulla, and the skin immediately removed before the 

 condition of " shock" had passed off, and therefore without any reflex 

 movement and concomitant secretory action. Such skins are termed 

 " normal." To obtain skins in the highest phase of secretory action, 

 the headless or intact fish (usually caught in summer) was either 

 exposed to the action of the vapour of chloroform, which acts at first 

 as a powerful stimulant, subjected to faradisation, or allowed to 

 writhe and slime in the manner common to Eels. Skins from such 

 fish are designated "stimulated." 



An examination of the slime of an Eel reveals the following histo- 

 logical elements : 



Fibres from 2 ft in breadth to the finest fibrils, inexcitable by 

 electricity, indigestible by acid pepsin or alkaline trypsin, giving the 

 xanthoprpteic reaction, and staining brilliant yellow with picro- 

 carmine. They are probably chemically of the nature of keratin. 

 These fibres resemble in microscopic appearance those of the slime 

 of Myxine, and from Eels placed in baths of pilocarpine solution are 

 often obtained in convoluted masses. 



Granules from 0*5 p, to 0*75 ytt in diameter, soluble in 5 per cent, 

 acetic acid, giving the xanthoproteic reaction, swelling, but not dis- 

 solving, in dilute alkali, resisting peptic and tryptic digestion, and 

 staining red with picrocarmine. 



Nuclei from 2 /i to 4*5 /* in diameter. 



Epidermic cells, and occasionally extruded goblet cells. 



In addition, mucin is present in the slime, seeing that the aqueous 

 extract boiled for several hours with 2 per cent, sulphuric acid yields 

 a substance capable of reducing Fehling's fluid, and is moreover pre- 

 cipitated by acetic acid. The acetic acid precipitate, however, being 

 partly soluble in excess of acetic acid, and leaving an insoluble 

 residue after digestion with pepsin and hydrochloric acid, it is prob- 

 able that nucleo- albumin may also be present, though sufficient 

 material for a phosphorus analysis was not collected. 



Histology of the Normal Epidermis. This has been studied by 



