JOURNAL OF MICROSCOPICAL SCIENCE. 



DESCRIPTION OF PLATE IV, 



Illustrating Mr. Clarke's paper on Nerve-structure. 



Fig. 



1. — Represents an elevation or ridge of the white substance on the surface 

 of a primitive nerve-fibre. 



2. — A double-contoured primitive-fibre, hardened in chromic acid, and mag- 

 nified 670 diameters. 



3. — A similar fibre treated in the same way, but with its outer corrugated 

 surface more or less broken. 



4 & 5. — Two detached portions of a fibre, hardened in chromic acid, 

 showing how the angular bendiugs give rise to the appearance of 

 fibres or tubules. 



6. — An uninjured double-contoured primitive-fibre, examined immediately 

 after death ; a, axis-cylinder ; b, outer contour ; c, inner contour ; 

 d, membranous sheath bearing an elongated nucleus. 



7 to 10. — Represent fresh primitive-fibres, more or less injured by mani- 

 pulation. 



11 to 16. — Represent the white substance of Schwann, between the 

 double contour, after injury by manipulation. At fig. 14 it appears 

 twisted in some places into a kind of knot ; while in other places it 

 is simply affected by indentations of various lengths and breadths, 

 which are represented by the dark spaces, the light spaces having 

 the appearance of fibres. 

 17 to 20. — Represent perfectly fresh primitive-fibres, stretched and other- 

 wise injured in manipulation, by which the white substance has been 

 thrown into variously-shaped convolutions, ridges, or apparent fibres 

 21. — Represents free globular contents escaped from the nerve-fibres. 

 22 and 23. — Two fresh nerve-fibres thrown into ridges of various shapes 

 and sizes, under the influence of strong acetic acid. In fig. 23, on 

 the surface of the fibre, are two or three spiral ridges similar to the 

 spirals seen at the cut end of fibres hardened in chromic acid. 

 24. — a, free nuclei from the connective tissue and sheaths of the nerve- 

 fibres in the white columns of the spinal cord ; b, nucleated cells from 

 the same parts in the calf; c, cut ends of two primitive nerve-fibres, 

 hardened in chromic acid, and presenting the appearance of spiral 

 fibres. The angular interspace between them is occupied by a 

 nucleated cell. 



