Sutlaii J II 111 MetalxAism (Did Inheritance l6j 



neutral soaps do have the power to dissolve Alkanna, Lackroth 

 and Sudan. It may be pointed out that Sitowski ('05) repeated 

 Hofbauer's error although he based no conclusions upon it. White- 

 head ('09) without knowing of Hofbauer's work attempted to solve 

 the same problem in a like manner. Mendel ('09) has shown that 

 Whitehead was further mistaken in his observation that after a dog 

 has been fed with Sudan, the lymphatics. of his mesentery remain 

 unstained. It may be stated here that there is no difficulty vvhat- 

 ever in finding the stain in the lymphatics of fowls, if these be 

 examined two or more hours after being fed the dye. 



Michaelis ('oi)made very careful chemical studies of Sudan and 

 related compounds. He considers the staining of fat a phvsical 

 and not a chemical process, and draws the conclusion from his 

 work that the physical properties of a bodv depend upon its chem- 

 ical character since the dye molecules, to be soluble in fat, must 

 have a very definite constitution. He concludes, "fat will be 

 stained by those azo-dyes which are 'indifferent' in the sense of 

 possessing no salt-forming groups. " Mann ('02) has given some 

 consideration to the nature of the union of Sudan with fatty com- 

 pounds, and on the basis of Michaelis' studies, states (p. 310) 

 that "the union between Sudan HI and oleic acid is a chemical 

 one depending on the oxidation of the unsaturated fatty com- 

 pound. Therefore, the action of Sudan III and similar dyes is 

 analogous to that of osmium tetroxide, the only difference being 

 that azo-dyes form additive compounds with the fat without 

 loss of color, while osmium tetroxide, after having formed addi- 

 tive compounds, is readily decomposed owing to the high valency 

 of the osmium." From either view-point, or indeed from any 

 possible viewpoint, it seems certain that the dye is bound to the 

 fatty constituents, cannot loosen from them, and is dragged with 

 them mechanically, so to speak, wherever they may go. 



(3) The Uses to ivhich Sudan has been applied in Experimental 



Biology and Medicine 



As has been noted, Daddi introduced the stain into histo- 

 logical work, used it as an intra- vitam stain, and by its means stud- 

 ied the foci and extent of various fatty degenerations of the liver 



