EXPLANATION OF PLATE 5 (CONTINUED) »' 



with but slight differentiation, the neurofibrils and the mitochondria staining 

 exactly the same color. The clear, uncolored spaces within the cell may consti- 

 tute the canalicular apparatus, because it is demonstrated, in a similar manner, 

 by this technique applied to adult spinal ganglion cells (Cowdry, '12 a, fig. 1). 



22 Apolar cells bordering the central canal of the neural tube opposite the 

 posterior part of the third somite from an embryo of 33 somites, length 8.3 mm. 

 and 74 hours incubation, prepared by Paton's modification of the Bielschowsky 

 method. The circumnuclear neurofibrillar network are shown in black (p. 403) ; 

 compare this with Cajal 1907, figures 1 and 2. 



23 Pear-shaped neuroblast isolated from the neural tube opposite the tenth 

 somite on the right side of an embryo of 25 somites, length 7.45 mm., stained in- 

 travitam in a 1 : 10,000 solution of janus green in 0.85 per cent sodium chloride so- 

 lution. The magnification is less, so that the granular mitochondria, shown in 

 green, seem smaller than in the other illustrations (p. 491). 



24 Cells from the same region of the same embryo stained in the same way, the 

 sole difference being the substitution of ocular 6 in place of compensating ocular 

 4 in making the drawing. Mitochondria bluish green. The cell walls are quite 

 distinct (p. 401). 



25 Taken from the dorsal portion of the neural tube of the same embryo as 

 figure 21, prepared by the same method and mounted on the same slide. The 

 process from the cell (a) is closely applied to that from the cell (b), both piercing 

 the membrana limitans externa together. The differentiation has been carried 

 to an extreme so that the neurofibrils have completely lost all shade of acid fuch- 

 sin and have assumed the blue color of the differentiator, toluidin blue, whereas 

 the mitochondria still retain their original bright crimson coloration. The neu- 

 rofibrils and the mitochondria are seen side by side in the processes of both cells 

 differentially stained. The clear spaces in the cell (b) may, as in figure 21, rep- 

 resent the canalicular apparatus (p. 410). 



26 Section from the same embryo, slide and method, which was also taken 

 from the dorsal part of the neural tube. The process from the cell (a) pierces 

 the membrana limitans externa and extends among the spinal ganglion cells {g. sp.). 

 The differentiation is here intermediate between that represented in figures 21 

 and 25. The neurofibrils have consequently lost their bright crimson coloration 

 (fig 21) and have become a brownish red color so that they may readily be distin- 

 guished from the mitochondria which are in the interfibrillar substance in the 

 cell process. A few clear, tortuous, uncolored spaces are seen in the spinal gang- 

 lion cell (g.sp.) which are possibly the canalicular apparatus (p. 410). 



27 A portion of the radix anterior from an embryo, length from the cervical 

 flexure to the tail flexure 8.4 mm., period of incubation 100 hours, corresponding 

 closely in degree of differentiation to Duval's embryo of 96 hours, which has been 

 stained by Bensley's anilin fuchsin methylene blue erythrosinate method. The 

 sheath cells (a) are shown and the mitochondria within them. The neurofibrils 

 appear a yellowish brown color and a few bright crimson mitochondria are visible 

 in the interfibrillar substance (p. 410). 



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