PLATE 6 



EXPLANATION OF FIGURES 



21 Cross-section of fiber of nervus ischiadicus of fowl Xo. 54. A new 

 axis cylinder, a, lies adjacent to the old, «', which still contains neurofibrillae. 

 m, a globule of degenerated myelin. Phosphomolybdic acid hematoxylin. X 555. 

 (See also fig. 23.) 



22 Cross-section of fiber of nervus ischiadicus of fowl No. 38. a, new 

 axis cylinder with newly formed medullary sheath, s; a', remnants of old axis 

 cylinder; n, neurilemma sheath; c, connective tissue fibrils. Phosphomolybdic 

 acid hematoxylin. X 1000. (See also fig. 24.) 



23, 24 and 26 Photomicrographs respectively of the same fibers shown in 

 figures 21, 22 and 25. Zeiss 4X2 mm. oil immersion. 



25 Cross-section of fiber of nervus ischiadicus of fowl No. 54. Two new 

 axis cylinders, a, are seen within the old myelin sheath, m, and in the position 

 previously occupied by the old axis cylinder. Each has acquired a secondaiy 

 myelin sheath. Phosphomolybdic acid hematoxylin. X 1000. (See also fig. 26.) 



106 



