YOLK. 599 



the following composition: C 53.42, H 7.63, N 15.63, O 22.19, S 0.41, P 0.43 per 

 cent. It also contains iron. The ichthulin investigated by LEVENE from codfish 

 eggs had the composition C 52.44, H 7.45, N 15.96, S 0.92, P 0.65, Fe + 22.58 

 per cent, and yielded no reducing substances on boiling with acids. The pure 

 vitellin isolated by HAMMARSTEN 1 from perch eggs had a similar behavior and 

 was very readily changed by a little hydrochloric acid so that it was converted 

 into a typical pseudonuclein. The codfish ichthulin yielded a pseudonucleic acid 

 with 10.34 per cent phosphorus, but this acid still gave the protein reactions. 



The yolk also contains albumin, besides vitellin and the above-men- 

 tioned proteins. 



The fat of the yolk of the egg, LIEBERMANN 2 claims, is a mixture 

 of a solid and a liquid fat. The solid fat consists chiefly of tripalmitin 

 with some tristearin. On the saponification of the egg-oil LIEBERMANN 

 obtained 40 per cent oleic acid, 38.04 per cent palmitic acid, and 15.21 

 per cent stearic acid. The fat of the yolk of the egg contains less carbon 

 than other fats, which may depend upon the presence of monoglycerides 

 and diglycerides, or upon a quantity of fatty acid deficient in carbon 

 (LIEBERMANN). The composition of yolk fat is dependent' upon the 

 food, as HENRIQUES and HANSEN S have shown that the fat of the food 

 passes into the egg. 



The phosphatides of the yolk seem to be of various kinds. THIER- 

 FELDER and STERN have found three different phosphatides. One of these, 

 which was soluble in alcohol -ether, behaved like lecithin. The second 

 was difficultly soluble in alcohol but readily soluble in ether, contained 

 1.37 per cent N and 3.96 per cent P. The third was a diamido phos- 

 phatide soluble with difficulty in ether but obtained in crystalline needles 

 from hot alcohol and contained 2.77 per cent N and 3.22 per cent P and 

 had a melting point of 160-170 C. FRANKEL and BOLAFFIO 4 also found 

 a substanoe crystallizing from hot alcohol and insoluble in ether with 

 2.78 per cent N and 2.18 per cent P. They call this body neottin and claim 

 that it is a triamido-monophosphatide having the formula Cg^^NaPOis. 

 BARBIERI has obtained a sulphurized phosphatide called ovin, con- 

 taining 1.35 per cent P, 3.66 per cent N and 0.4 per cent S. The 

 relation of all these bodies to each other must be further studied. 



Lutein. Yellow or orange-red amorphous coloring-matters occur in 

 the yellow of the egg and in several other places in the animal organism ; 

 for instance, in the blood-serum and serous fluids, fatty tissues, milk- 

 fat, corpora lutea, and in the fat-globules of the retina. These coloring- 



1 Walter, Zeitschr. f. physiol. Chem., 15; Levene, ibid., 32; Hammarsten, Skand. 

 Arch. f. Physiol., 17. 



2 Pfliiger's Arch., 43. 



3 Skand. Arch. f. Physiol., 14. 



4 Thierfelder and Stern, Zeitschr. f. physiol. Chem., 53; Friinkel and Bolaffio, 

 Bioch. Zeitschr. , 9; Barbieri, Compt. rend., 145. 



