YOLK AND WHITE OF THE EGG. 155 



lecithin, but it is not known whether this is chemically com- 

 bined with the nucleoalbumin, vitellin, or only adheres to it. 

 Place the precipitate in a flask and boil on the water-bath 

 with absolute alcohol, filter, wash with alcohol, then with 

 ether, and finally grind in a mortar or place in a vacuum desic- 

 cator over sulphuric acid to remove the ether. A fine white 

 or light-yellow powder, which contains only 0.95 per cent, of 

 phosphorus, is obtained. Its solubility is essentially differ- 

 ent from that of the first precipitate, which still contains 

 lecithin; presumably the vitellin is coagulated by boiling 

 with alcohol. No method is yet known by which the vitellin 

 may be freed from lecithin without coagulating it. 1 



The alcoholic solution yields on evaporation on the water- 

 bath a yellow viscous residue which consists essentially of 

 lecithin. 



(b) THE WHITE OF THE EGG. 



The albumen or white of the egg consists principally of a 

 concentrated solution (about 11 to 12 per cent.) of a specific 

 proteid, ovalbumin or egg-albumin, which is enclosed in a net- 

 work of membranes much less in quantity. Besides the egg- 

 albumin there are also present very small quantities of a 

 globulin, also ovomucoid, glucose, and inorganic salts. 



I. Reactions of Egg-Albumin. 



For these reactions shake vigorously 20 cc. of albumen 

 with 150 cc. of water in a flask and then filter. The solution 

 (about 1.5 per cent.) must be clear or only faintly opalescent. 

 The first portions of the filtrate arc frequently turbid; these 



1 It might be supposed that vitellin could be prepared in connection 

 with the separation of the yolk of egg into its constituents given under I, 

 but it has been found that this is generally not advantageous, as the 

 residue left when large quantities are worked up does not as a rule dis- 

 solve easily in sodium chloride solution; presumably this is due to the 

 length of the treatment. 



