METHYLEN BLUE. 231 



there may be obtained a specific stain of axis-cylinders of 

 sensory nerves. He held, and it has long been held by 

 observers, that the stain so obtained is a product of a vital 

 reaction of the tissues, and that it cannot be obtained with 

 dead material. From the point of view maintained in 201 

 the contrary would be the real state of the case. The stain 

 is, of course, an intra-vitam phenomenon, in so far as it takes 

 place during the life of the organism ; but I hold that the 

 tissue itself does not take on the stain till it is dead or patho- 

 logically affected. 



As said before, it was formerly held that the reaction 

 could not be obtained with dead material. DOGIEI., however 

 (Arcli.f. iniJi. AnaL, xxxv, 1890^ pp. 305 et seq.), found that 

 muscle nerves of limbs of the frog could be stained as much 

 as from three to eight days after the limbs had been removed 

 from the animal. He concludes, indeed, that the reaction 

 shows that the nerves were still living at that time. But it 

 seems more natural to conclude with APATHY (Zeit. f. ?r/.s>. 

 Mill., ix, 1, 1892, pp. 15 ct *v<[.} that nerve tissue can be 

 stained after life has ceased. 



APATHY has directly experimented on this point, and sum> 

 up the necessary conditions as follows : The tissue need not 

 be living, but must be fresh ; nothing must have been 

 extracted from it chemically, and its natural state must not 

 have been essentially changed by physical means. For 

 example, the tissue must not have been treated with even 

 dilute glycerin, nor with alcohol, though a treatment for a, 

 short time with physiological salt solution is not very hurtful ; 

 it must not have been coagulated by heat. 



Another common belief concerning the methylen-blue 

 nerve reaction is that the presence of oxygen is necessary to 

 the reaction. Jt is, therefore, the usual practice to dissect 

 out the organ to be investigated after having exposed it to 

 the action of methylen blue by injection or immersion, and 

 leave it for some time exposed to the air. APATHY has also 

 investigated this point, and finds (lac. cit., p: 25) that the 

 practice is in some cases correct, but the belief erroneous. 

 His point of view is that the stain is a regressive one. It has 

 been explained above that shortly after a tissue has attained 

 the maximum degree of coloration of which it is susceptible 

 it begins to give up its colour again to the surrounding liquid. 



