462 



ELEMENTARY PHYSIOLOOY 



LESS. 



FlO. 146.— To ILLUSTRATE THE STRUCTURE OF NeRVE-FIBRES. 



A. A nerve-fibre seen without the use of reagents, showing the "double 

 contour" due to the medulla, andn, a node. Neither axis-cylinder nor 

 neurilemma can be distinctly seen. (Magnified about 300 diameters.) 



B. A thin nerve-fibre treated with osniic acid, showing, nc, nucleus 

 with protoplasm, p, surrounding it, beneath the neurilemma ; n n, the 

 two nodes marking out the segment to which the nucleus belong.s, 

 (Magnified 400 diameters.) 



C. Portion of fibre (thicker than B), treated with osmic acid to show 

 the node n; m, the densely stained medulla; at m' the medulla is seen 

 divided into segments. (Magnified 350 diameters.) 



I). Portion of nerve-fibre treated to show the passage of the axis- 

 cy'inder, nx, through the node, n ; m, the medulla. At nx' the axis- 

 cylinder is swollen by the reagents employed and large and irregular. 

 (Magnified 300 diameters.) 



E. Portion of nerve-fibre treated with osmic acid, showing the nucleus, 

 nc, embedded in the medulla; c, fine '.:erineurial sheath lying outside 

 the neurilemma ; the outline of the latter can only be recognised over 

 the nucleus nc ; the nucleus, nc', belongs to this perineurial sheath. 

 (Magnified 400 diameters.) 



F. Portion of nerve-fibre deprived of its neurilemma and showing the 

 medulla broken up into separate fragments, m m, surrounding the axis- 

 cylinder, nx. 



