CAROTIN, THE PRINCIPAL YELLOW PIGMENT OF MILK FAT. 325 



claims to have found it, or was able to show all the properties which 

 he describes for the crystals which he evidently did obtain. 



Crystalline animal pigments were apparently obtained before 

 Thudichum's claims in this regard. According to Krukenberg, 1 Wittich 2 

 obtained crystals of a red pigment from Euglenia Sanguirubo, and 

 Piccolo and Lieben 3 found a crystalline animal pigment. Pouchet 4 

 a little later obtained a yellow crystalline pigment from lobsters. 



The Chromophanes. The early workers in the field of animal pig- 

 ments laid great emphasis upon the so-called color reactions, one of 

 which, the blue reaction which concentrated HNCX, was mentioned by 

 Thudichum. That a similar reaction is given by concentrated H 2 SO 4 

 was first noticed by Wittich in 1863, an< ^ Buchholz also noticed it with 

 a fat pigment from a Ganglion cell of an invertebrate. Piccolo and 

 Lieben had also noticed the blue reaction with concentrated H 2 SO 4 . 

 Besides Thudichum, Filhol 5 and Stadeler Q noticed the blue reaction 

 with concentrated HNO 3 . Stadeler attempted to isolate the egg yolk 

 pigment. He failed to do so, however, but attempted to establish the 

 difference between it and Bilirubin with which it bad been considered 

 identical. A little later a third reaction of the luteins was discovered 

 by Schwalbe, 7 namely a blue-green color with a solution of iodine in 

 potassium iodide. Schwalbe first noticed the reaction with the cone- 

 globules of the retinas of birds and lizard's eyes. The red globules 

 gave a beautiful blue to blue-black color, and the yellow oil globules a 

 green to blue-green to blue. The pigments thus characterized were 

 called chromophanes by Schwalbe and the existence of these pigments 

 was a little later considerably extended by Capranica 8 who also made 

 use of the iodine reaction. 



Kiihne 9 took up the study of the chromophanes of the cone- 

 globules of bird retinas, and separated three pigments which he desig- 

 nated Rhodophan, Chlorophan and Xanthophan, respectively, according 

 to the color of their solutions. 



Kiihne also studied the absorption spectra and color reactions of 

 the pigment of the egg yolk and the corpus luteum and compared them 



1. Grundzuge einer vergleichenden Physiologie der Farbstoff und der 

 Farben; 1884. 



2. Arch f. Path. Anat. 27, p. 573 (1863). 



3. Giornals d. Scienze Natural! et. Economich. Palermo 2, p. 258 (1866). 



4. Jour. d. L'Anat et. Physiol. 12, p. 12 (1876). 



5. Compt. Rend. T. 39, p. 184, T. 50, pp. 545 and 1182. 



6. Jour. f. Pract. Chem. 100, p. 149 (1867). 



7. Hand D. Ges. Augenheilkunde von Graefe u. Saemisch I, p. 414 (1874). 



8. Arch. f. Anat. Physiol. p. 283 (1877). 



9. Untersuch, des Physiol. Universitat Heidelberg I, 4th Heft, p. 341 

 (1878); IV, p. 169 (1882); Jour. Physiol. 1, p. 109 (1878). 



