SO METHYLEN BLUE, AND OTHER ANILINS. 



earlier or later than the maximum. Or the observer may fix 

 the stain in either of these stages and preserve it for leisurely 

 study by means of one of the processes given below under 

 the heading " Preservation of the Preparations." 



The proper strength of the very dilute solutions to be 

 employed in the manner here considered must be made out by 

 experiment for each object. I think the tint is practically a 

 sufficient guide, but it may be stated that when in doubt a 

 strength of 1*100000 may be taken, and increased or di- 

 minished as occasion may seem to require. ZOJA (Eendic. R. 

 1st. Lombardo, xxv, 1892 ; Zeit. f. wiss. Mik., ix, 2, 1892, 

 p. 208) finds that for Hydra the right strength is from 

 1-20000 to 1-10000. 



The stain is somewhat capricious. It is not possible to 

 predict without trial which tissues will stain first in any 

 organism. It is to be remarked that the stain penetrates 

 very badly, which is perhaps the chief cause of its seeming 

 capriciousness, and, I take it, the chief determining condition 

 of the order in which tissues stain. Gland-cells generally 

 stain early ; then, in no definable order, other epithelium- 

 cells, fat-cells, plasma-cells, ' Mastzellen/ blood and lymph 

 corpuscles, elastic fibres, smooth muscle, striated muscle. 

 There are other elements that stain in the living state, but 

 not when the staining is performed by simple immersion of 

 intact animals in a dilute staining solution in the manner we 

 are considering. Chief amongst these are nerve-fibres and 

 ganglion-cells, which remain unstained in the intact organism, 

 most likely, so far as I can see, for the simple reason that the 

 stain is not able to penetrate them. 



115. Staining Nerve-tissue during Life, It is commonly 

 believed that methylen-blue stains of the class we are con* 

 sidering are the product of a vital reaction of the tissues, and 

 cannot be obtained with dead tissue. It would, however, 

 appear to be more correct to say that methylen blue has the 

 property of staining living tissue, not because of its being 

 living, but in spite of its being living. DOGIEL (Arch. f. mik. 

 Anat., 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 



