450 



SCIENCE 



[N. S. Vol. XXXIX. No. 1004 



the dye did not color the skin or mucous 

 membranes of the animal, this was eventu- 

 ally obtained. The study of an animal in 

 the early stage of such a series of injec- 

 tions is most interesting. We have indi- 

 cated that such a negative dye must consist 

 chiefly of large particles, and since little 

 color appears in the urine of these animals, 

 and the animal is externally unstained, it 

 is evident that the dye particles are en- 

 gulfed by cells internally located. The au- 

 topsy of such an animal shows that not only 

 the skin but most of its tissues are free 

 from dye with four notable exceptions; 

 namely the liver, the spleen, the lymph- 

 glands, and the bone marrow, all of which 

 are blue-black. 



We do not believe that a heightened 

 power to attract the dye is possessed by the 

 cells in these localities. The skin cells in 

 the neighborhood of a puncture take up the 

 stain almost as rapidly, but they are un- 

 able to do it when the large dye particles 

 are only circulating in the blood vessels, 

 from which their lack of diffusion powers 

 never take them, for they can not leak 

 through the walls of the capillaries. 



A glance at the list of positive and nega- 

 tive dyes which is just presented shows us 

 that most positive dyes are disulfonie 

 acids, a statement, in view of the ideas 

 which we have just developed, which means 

 that the sulfonic acid radicle exerts a 

 favorable effect on the character of the dye 

 solution, i. e., makes it more soluble, more 

 diffusible, and, so, quickly distributed, that 

 is, a true' vital stain. Evidence to this ef- 

 fect has already accumulated in a compari- 

 son with the positive and negative dyes 184, 

 185, 1846, 1824 and 1835, but this conclu- 

 sion is, we think, substantiated in a more 

 complete and overwhelming way by the 

 sulfonation of a number of negative dyes 

 by which means brilliant, positive stains 

 were always secured. We cite as a good 

 example of this 



HjnI 



;X>=. 



JSOsNa 



NaOsSi 



I I 



negative 

 ON __ OH 



SOsNa NaOaSi 



>N = Nr 



OsNa 



positive 



NaOsS' 



NHj 



/SOsNa NaOsSs 



brilliant positive 



Identical results were secured with the 2.8 

 amido naphtol 6 sulfonic acid combined 

 with benzidine, with benzidine monosul- 

 fonic acid and with benzidine disulfonie 

 acid; and a similar effect of sulfonation is 

 seen in the brilliant tetra-sulfonic congo 

 red dye made from the 1 naphtylamine 4.8 

 disulfonie acid, whereas the congo red 

 monosulfonic acid (the 1 naphtylamine 4 

 sulfonic acid) or naphtionic acid yields a 

 dye which is not a vital stain. 



NHj 



I I 



SOaNa 

 NaOsS NH2 



I I 1 



SOsNa NaOaS 



brilliant positive 



In this connection the question of whether 

 or not it was possible to over-sulphonate the 

 dye was attempted with interesting results. 

 The sulfonation of diamine blue 2B gives 

 us a dye which while a vital stain neverthe- 

 less passes the kidney much more rapidly 

 than the original body, so that after an in- 

 tense stain the animal is decolorized again 

 in a few days. We have secured identical 

 results in experiments with a similar sul- 

 fonated trypan blue. 



