1 66 Oscar Riddle 



Follicular epitheliLun: birds, reptiles, mammals, (Riddle, '07 b). 

 Epithelium of nianiDiary glands: rat, (Gage, Stotsenberg,'o8 b). 

 Theccee of Corpus luteutn: rabbits, (Riddle, this paper). 

 Peritoneum: birds, (Riddle, this paper). 



(2) The Mechanism of the Transfer and Deposi ion of Sudan 



within the Body 



Practically all we know concerning the mechanism of the 

 transfer and deposition of Sudan we owe to the feeding experi- 

 ments and observations of Daddi, to the studies on the solubility 

 of the stain by Pflii'ger and Nerking, and to the chemical researches 

 of Michaelis. 



Daddi ('96) found that when fed to rabbits, gumea-pigs, pigeons 

 and fowls, Sudan passes through the intestinal epithelium, enters 

 the circulation and is deposited in the adipose tissue of the body 

 generally; that it is a specific fat strain, and that in its introduc- 

 tion and deposition in the body it is always associated with fat. 

 Biedermann, ('98) was the next to use Sudan experimentally. He 

 fed the stain to Tenebrio molitor and found that although the 

 intestmal contents became colored, the body fat was not colored.^ 

 Hofbauer ('00) made the mistake of supposing that only natural 

 fat and not soap .and fatty acids, was able to carry the dye 

 through the intestinal epithelium, (he used Alkanna which re- 

 sembles Sudan in its solubilities, and he also refers to Sudan). He 

 thought, therefore, that by use of the stain he could determine 

 in which form the fats are absorbed from the intestine. The 

 paper containing this error, two other papers which repeat it, 

 together with the three or four papers devoted to exposing the 

 error, furnish nearly one-half of the literature dealing with Sudan 

 HI. Pfli-iger ('00) and Friedenthal ('00) simultaneously pointed 

 out Hofbauer's mistake, showing that under the conditions furn- 

 ished by the intestine Sudan is soluble not only in fat but in bile, 

 in sodium soap and in glycerine. Friedenthal, however, declared 

 that soaps have no power to dissolve the stain in the absence of 

 free fatty acids. Nerking ('00) immediately showed that entirely 



' Prof T. H. Morgan informed the writer that in a fly, Drosophila, he has recently obtained a simi- 

 lar result. 



