444 



SCIENCE 



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



that the study of dyes which suffer no 

 chemical change within the body is of the 

 highest value and indeed calculated to lead 

 us to results which can be secured in no 

 other way, we do so mainly because the 

 class of dyes to which we refer can be in- 

 jected in relatively large quantities into 

 the blood stream of living animals without 

 perceptible toxic effect; and the dye, taken 

 care of as it were by definite cells which 

 store it unchanged within their cytoplasm, 

 can be detected without difficulty, wherever 

 it may be, on account of its color. 



In 1905, Ehrlich and Shiga, then at- 

 tempting the cure of trypanosome infec- 

 tions in laboratory animals, happened to 

 find that the azo dye, which they named 

 trypan red and which possesses the follow- 

 ing formula: 



NaOsS!, 



JSOaNa 



could be injected in sufficient quantity into 

 the living animal to kill the organisms of 

 the disease without perceptible toxic effect 

 to the cells or tissues of the host, them- 

 selves deeply stained. A year later, driven 

 thither in the same quest, NicoUe and Mes- 

 nil, of Paris, discovered a similar effective 

 compound or "good color" as they called 

 it in trypan blue, a dye formed by the 

 combination of two molecules of 1.8 amido- 

 naphtol 3.6 disulphonic acid with one mole- 

 cule of diazotized ortho-tolidine in alkaline 

 solution. 



OH NHa 



NHz OH 



CH. CHj 



The profound color of the healthy animals 

 which received this dye could not fail to 

 attract the attention of Nicolle and Mesnil, 

 who set Boufard the fascinating problem 



of determining in what form the dye per- 

 sisted in the body. His report, which was 

 all too short, nevertheless acquainted us 

 with the main fact that the dye had not 

 merely remained in the fluids of the body 

 or had pervaded the organs and tissues in 

 a profuse way, but was engulfed in the 

 bodies of certain definite cells primarily of 

 one type which we shall have occasion to 

 describe carefully shortly. Coincidently 

 Goldman at Ehrlich 's suggestion took up 

 the same theme, and his enthusiastic studies 

 have in spite of occasional inaccuracy at- 

 tracted general interest to the subject. 



Nowhere however in the rapid literature 

 which has begun to accumulate on this sub- 

 ject can one fijid an attempted answer to 

 the fundamental question of how the dye 

 really acts on the cells of the body, i. e., 

 what property it is by virtue of which one 

 of the members of this class of dyes is en- 

 abled to be a brilliant vital stain; whereas 

 a closely related dye is a complete failure. 

 Nor, secondly, does it seem to me that full 

 advantage has been taken of the great op- 

 portunity bestowed by these dyes in ena- 

 bling us to detect a hitherto unknown or un- 

 recognized function of a great mass of cells 

 all over the body which can now be grouped 

 together under a common designation as a 

 great system or tissue. 



If we inject into the peritoneal cavity of 

 a mouse 1 c.c. of a one half per cent, solu- 

 tion of trypan blue, we can observe within 

 a few minutes that the ears, the tip of the 

 nose, the tail, the mucous membranes and 

 soon the skin of the entire body have begun 

 to blue, and that this deepens rapidly in 

 intensity, so that within a few hours a 

 maximal deep blue color is possessed by the 

 animal, a color which, in spite of this single 

 dose, is not lost for many weeks. The ani- 

 mal thus stained plays, eats, breeds, and in 

 all ways manifests its normal activity, and 



