314 JAMES EDWARD ACKERT 



and 0.4,u in width to 0.9/i in length and O.S/x in width. In the 

 sections studied, these end-knobs appear to be numerous. Ordi- 

 narily, one to a cell is observed, though occasionally even two 

 are seen close to a single cell boundary. Sometimes a tiny fibril 

 appears to end without any enlargement (fig. 7, x) . This, however, 

 may be due to the failure of the methylene blue to differentiate 

 the end-knob, as those who have worked with this stain will 

 readily understand. 



That these diminutive enlargements or end-knobs are real 

 nerve terminations and not the nodal swellings sometimes seen 

 where fibers divide has been satisfactorily proven. For example, 

 in focusing on the surface of the transparent stratum corneum 

 no knobs nor fibrils can be seen. A deeper focus brings into 

 view end-knobs with a fine nerve fibril running into each. A 

 still deeper focus shows tissue below the end-knobs and enables 

 one to follow the nerve fibrils from the now indistinct terniinal 

 swellings back to the branch from which the nerve fibrils are given 

 off. Where Kttle or no pigment is present, these nerve termi- 

 nations can be seen without difficulty. 



For a time the writer was unable to determine whether the 

 nerve end-knobs are situated in the stratum Malpighii or in the 

 deepest layers of the stratum corneum. At length, however, 

 a section was found in which a part of the ventral surface of the 

 interfemoral .membrane curled up, permitting an oblique view. 

 The methylene blue stain was deep enough to show the margins 

 of a number of consecutive superficial cells of the stratum granulo- 

 sum (fig. 6), and little pigment was present. By focusing upon 

 this obliquely turned portion of the surface of the membrane, it 

 was comparatively easy to distinguish the flat, elongate, scale- 

 like cells constituting the stratum corneum from the more oval, 

 clearly defined, superficial cells of the Malpighian stratum. By 

 focusing upon the curved surface it was possible to see a number 

 of nerve end-knobs on or near the surface of the stratum granu- 

 losum, but as yet no end-knobs have been seen by the writer in 

 the stratum corneum. 



The question of the exact position of the end-knobs in respect 

 to the epithelial cells naturally arises. It is certain that a large 



