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J. B. JOHNSTON. 



middle line, diverging more or less. The fibers which remain on 

 the same side separate into two ill-defined bundles, of which the 

 one nearer the median line consists of the fibers. The medium 

 and coarse fibers are situated laterally. In a high focus, some- 

 what above the root of the nerve, a distinct bundle of fibers is 

 seen running along dorsal to and independent from the spread- 

 ing fibers of each nerve. Some fibers of each nerve, however, 

 enter this bundle. The bundle consists of medium coarse fibers 



FIG. 7. A diagrammatic transverse section of the nerve cord and a dorsal root. 

 The sheath of the nerve cord is marked with oblique lines. The right lateral group 

 of giant fibers, the mid-ventral fiber and one pigment cell are shown. The stippled 

 area shows the position and size of the compact dorsal bundle of fibers as it appears 

 in the middle region of the body. The disposition of the coarse and fine fibers and 

 their ganglion cells and the position of one viscero-motor cell are shown. 



and is situated at the surface of the cord between the mid-dorsal 

 line and the nerve roots. Its position is shown in Figs. 6 and 7. 

 This bundle is distinctly seen in haematoxylin sections but has a 

 very different appearance after different fixing agents. It is not 

 well fixed in all fluids. In Zenker's fluid it contracts and the 

 fibers become aggregated into a dense mass which is surrounded 

 by an open space. In twenty per cent, formol the bundle has 

 the appearance of poor fixation with swelling. It appears as a 

 lightly stained reticulated area in which the fibers are not sharply 

 visible. In both these fluids the remainder of the cord seems to 

 be well fixed and stains well. In Worcester's fluid, which has 



