274 THE PHYSIOLOGY OF REPRODUCTION 



Liebermann records a loss of nitrogenous substances in bis 

 analysis of bens' eggs at various stages of development ; but as 

 Hasselbalcb ^ pointed out, tbis loss is accounted for by tbe egg- 

 membrane, wbicb is left bebind wben tbe cbick is batcbed, and 

 wbicb was not included in Liebermann's analysis. 



Reference bas abeady been made to nitrogenous consti- 

 tuents of tbe yolk : tbe two pbospboproteins vitelbn and livetin. 

 Tbe otber protein substances of tbe wbite of tbe egg can be 

 distinguisbed according to tbeir reactions as albumens, globuUns, 

 and a substance bebaving like a peptone in so far as it is not 

 coagulated by beat and not precipitated by ammonium sulpbate or 

 by bydrocbloric and acetic acids. According to tbe investiga- 

 tions of Morner,^ tbis substance is a true glucoprotein and belongs 

 to the mucoid substances. It bas, therefore, received tbe name 

 Ovomucoid. On boibng witb bydrocbloric acid it yields 34 per 

 cent, of glucosamine.^ Tbe amount of ovomucoid present in tbe 

 wbite of tbe egg is about 10 per cent, of tbe proteins ; 6 per 

 cent, of tbe proteins belong to tbe globubn group, tbe remainder 

 being tbe albumens. All tbe proteins of tbe wbite of tbe egg, 

 not only tbe ovomucoid, are exceptionally ricb in tbe carbo- 

 hydrate radicle, and on boibng witb dilute hydrochloric acid 

 yield considerable quantities of glucosamine. Tbe albumens 

 and globuhns contain about 10 per cent, of glucosamine. This 

 explains perhaps tbe almost complete absence of carbohydrates 

 in the egg. It acquires further significance from the fact that 

 tbe developing tissues of the embryo are very rich in mucin, a 

 protein containing considerable quantities of glucosamine. 



The globulin fraction of the egg-white has not yet been 

 studied in detail. It is probable that it is a mixture of several 

 globubns. 



The investigation of the albumen fraction has been greatly 

 facibtated by the work of Hofmeister * and Hopkins,^ which 



' Hasselbalcb, " fiber den respirator! sch en StofEwechsel des Hiihner- 

 embryos," Skandinav. Arch. f. Physiologie, vol. x., 1900. 



^ Morner, " Uber die Im HUhnereiweiss in reichlicher Menge vorkommende 

 Mucinsubstanz," Zeitschr. f. physiol. Chemie, vol. xviii. 



' Quoted from Ergebnisse der Physiologie, vol. i. , Part I. 



'■ Hofmeister, " Uber Krystallisatiou des Eialbumins," Zeitschrift fur 

 physiolog. Chemie, vol. xiv., 1890, and vol. xvi., 1892. 



^ Hopkins and Pinkus, "Observations on the Crystallisation of Proteids," 

 Journal of Physiology, vol. xxiii., 1898. 



