40 ON THE DIFFERENTIAL REACTION TO VITAL DYES EXHIBITED BY 



case of any one dye will influence greatly their rate and extent of decolorization. 1 

 Through our studies we now know that just as permanent dye effects may be se- 

 cured from some of the less colloidal, rapid-staining positive benzidine dyes as from 

 pyroll blue or any of the negative dyes, for we have merely to use frequent but very 

 low dosage to attain this result. The cellular deposits produced by much slower, 

 very dilute dosage enjoy a very much longer " post-experimental " life. The dye in 

 them is obviously less able to leave them and stream through the cell's protoplasm 

 to reach the extracellular juice. Or if decolorization be- due also to chemical de- 

 struction of dye depots, such denser depots withstand longer attack on the part of 

 the cell. It is unlikely that any part of the decolorization process consists in the 

 mechanical expulsion or separation of the dye from its vacuoles or of the dye vacuole 

 in entirety from the cell, such as we observe in the shedding of food vacuoles in 

 certain protozoa; for were this the case it would be difficult to see how differences 

 in the state of the dye within the vacuole could produce the observed differences 

 in the rapidity of the decolorizing process. There are, in fact, no other evidences 

 of such a purely mechanical expulsion of the dye deposits as constituting the decol- 

 orizing act. This material is never encountered just without the confines of the 

 cell. Indeed, other evidence convinces us that the dye escapes by diffusion from the 

 places of its detention within the cell. In the case of those dyes which, like T 148, 

 produce large segregation vacuoles in the fibroblastic protoplasm, the decolorizing 

 act leaves these cells practically free from dye but with the full number of the 

 dye-inclusion vacuoles filling the protoplasm. The decolorization phenomenon 

 thus furnishes one of the strongest reasons for believing that vital-staining effects 

 are produced by the cell's acceptance of substances which possess power of diffu- 

 sion ; for this would appear to be the best available explanation of the method of 

 egress of the dj'e from its intracellular depots. If the dye does leave its place of 

 agmination inside the cell by such processes, there is furnished all the necessary 

 proof that it could originally enter the cell by such means, and there exist no 

 grounds for the hypothesis that the azo dyestuffs can enter these cells only by 

 virtue of a truly phagocytic act. 



Nowhere does the contrast in behavior between macrophages and fibroblasts show 

 itself more emphatically than in the decolorization phenomena. The connective-tissue 

 producing cells not only show relatively less decolorization, but, if one will wait 

 long enough, will be found to have absolutely more dye in them than have their 



1 It is of interest to note that Goldlnnnn laid great weight on tlie necessity of a gradual rather than a rapid attainment 

 of a vital stain, lie railed particular attention to the great permanency characterizing staining by the slower method, 

 and felt that more normal conditions were secured by slow application, such as by the cutaneous method with pyroll blue. 

 Speaking of the "toxic" effect of dyes which, like trypan blue, tinged the whole animal speedily and intensely! (ioldmann's 

 impression has some basis in fact. It is possible to produce tissue new-growths merely by the application of larger doses of 

 the benzidine dyes (endothelial giant cells in the sinusoids of the liver, bone-marrow, and spleen), but dj es which stain more 

 quickly are not necessarily more toxic. Ease of decolorization, however, follows strictly ease of staining, and those vital 

 stains which are produced with speed with benzidine dyes fade with corresponding cilerily. Qecolorization need not be 

 allowed to occur, however, if one will only plan his dye dosage with appropriate relation to the time at which tissues are 

 to be examined for vital-staining elicits; and the greater speed of staining produced by the benzidines makes them indis- 

 pensable for some studies in which a slower method would not yield results. Goldmann's unfavorable opinion fortunately 

 did not induce Schulemann (1911!) to desist from his valuable studies on trypan blue, in which for the first time were shown 

 all the p.\ Toll-blue cell pictures, produced with greater ease, even if with less permanency, by intravenous dosage. It was also 

 quickly apparent to experimental workers like Gross, Wieszeniewski, MacCurdy, Evans, Winternitz and Bowman, and many 

 others, that in tissue changes of rapid history the application of the trypan class of dyes rather than the slowly acting dyes 

 would bo necessary in order to test the staining possibilities of altered or of new tissue components from time to time. 



