Editorial, T'cc/i/iiqnc and Mc/i/oranda. 105 



pineal eye was developed to function during the period of 

 metamorphosis, during which the organ adapted itself to the 

 new conditions? 



This theory may serve to explain the different course of 

 histogenesis pursued by the eye as compared with the other 

 organs of special sense. 



TECHNIQUE AND MEMORANDA. 



Methyl Blue Nerve Staining Intra-vitam. — The 

 various methods of injecting staining reagents into the 

 circulation depending on incipient degeneration of 

 the tissues or the access of air to precipitate or differentiate 

 the colors, have thus far promised more than they have ful- 

 filled. The most promising of these, the methyl-blue stain, 

 has received a searching analysis at the hands of Dr. B. 

 Feist. (') The process as introduced by Ehrlich, consists 

 simply in injecting into the nervous system (cutaneous vein 

 or lymph hearts in the frog) a concentrated solution in nor- 

 mal salt fluid. The difhculties chiefly grow out of the ten- 

 dency of the color to fade rapidly after development, but 

 these may be avoided by fixation in Hoyer's picrocarmine. 

 When used quite dilute and for not too long a time the blue 

 color is scarcely altered by its use while a longer action alters 

 the color to Burgundy red, or rusty red, while the nuclei of 

 adjacent cells are faintly tinted with rose. The exact reac- 

 tion which takes place in the nerve, after vital impregnation 

 with methyl blue and exposure to the air, is a matter of de- 

 bate. Aronson says, that during life nerves are so well supplied 

 with oxygen that the methyl blue absorbed by them cannot 

 be reduced. After the death of the animal nearly all the 

 colored portions, as well as the nerves, are rendered color- 

 less, because the affinity of the protoplasm for oxygen in- 

 creases to such an extent that the oxygen is abstracted and 



I Arch. f. Anat. u. Phys. 1890. Phys. Abtli. p. 116. 



