OCTOBEB 19, 1906.] 



SCIENCE. 



483 



pared from commercial benzol, magenta and its 

 train of colored derivatives would in all prob- 

 ability have remained unknown to the present 

 day from the simple fact that magenta can not 

 be produced from pure aniline, a second body 

 being also required. 



The industry thus initiated with a vio- 

 lent impetus soon showed its revolution- 

 izing tendencies and its vitalizing power 

 in almost every branch of human endeavor. 

 To-day about 2,000 individual dyestuffs 

 are known, giving the whole range of the 

 colors of the rainbow, and complying with 

 every demand of taste, fashion and stabil- 

 ity. They surpass in beauty and bril- 

 liancy the colors supplied by nature, and, 

 contrary to the impression prevailing 

 among the public, the shades obtained with 

 some of them are faster to the influence 

 of time, light and chemicals than the fastest 

 which nature produces. 



The greatest triumph of this branch of 

 the industry was the artificial production 

 of alizarine and indigo. In the technical 

 production of the former our distinguished 

 guest has played a prominent part, solving 

 the problem of its manufacture simultane- 

 ously with Graebe, Liebermann and Caro, 

 whose English patent antedates that of 

 Perkin by one day, and for the first syn- 

 thesis of indigo cinnamic acid was success- 

 fully employed which was originally ob- 

 tained from coal tar by Perkin. 



Coal tar colors, however, are not only 

 used for the dyeing of textile fibers, like 

 wool, silk, cotton, linen, jute, ramie, etc., 

 but for a host of other materials. 



The lady's hair is gray, or of a hue not 

 fashionable at the time — coal tar colors 

 will assist her in appearing youthful and 

 gay. In eating the luscious frankfurter 

 your soul rejoices to see the sanguineous 

 liquid oozing from the meat— alas coal tar 

 colors have done it, and friend Wiley can 

 prove it. The housewife selects a bright 

 green broom, on account of its anticipated 

 good wearing quality, but finds, to her 



sorrow, that coal tar colors furnished the 

 freshness. The product of the hen is re- 

 placed by yellow coal tar colors in custard 

 powders, and butter is colored yellow when 

 the dyestuff laboratory of the cow is on a 

 strike. Leather, paper, bones, ivory, 

 feathers, straw, grasses, are all colored, 

 and one of the most interesting applica- 

 tions is the dyeing of whole pieces of even 

 the bulkiest furniture by dipping them in 

 large tanks containing the dyestuffs, which 

 transforms the wood into walnut, mahog- 

 ony at your command, as carried out in 

 our big factories in Grand Rapids and else- 

 where. 



As coal tar colors are used on this 

 enormous scale, so they are also employed 

 in a liliputian manner, for staining speci- 

 mens for examination under the micro- 

 scope, enabling us to detect and identify 

 bacteria, the finest nerve-ends and other 

 minute elements of animal tissues, and by 

 means of such staining methods, especially 

 with methylene blue, Koch discovered the 

 bacillus of tuberculosis and cholera, and 

 initiated the modern battle against pre- 

 ventable infectious diseases. In reciproca- 

 tion for the excellent reagents supplied 

 him by the dye industry, the histologist 

 brought about the discovery of a new and 

 very important class of colors, and as this 

 instance is one of the most striking demon- 

 strations of the interdependence of prac- 

 tise and theory, I shall relate it to you. 

 In 1886 Ehrlich observed that methylene 

 blue and some of its congeners were the 

 only colors which stained the living nerve 

 tissue, and in order to determine whether 

 this remarkable property was due to the 

 peculiar constitution of methylene blue or 

 to the presence of sulfur, he found it de- 

 sirable to experiment with a substance 

 analogous to methylene blue, but in which 

 the sulfur was replaced by oxygen. He 

 applied to Dr. Caro requesting him to 

 assist him in his work by furnishing him 



