300 THE UNFERTILISED EGG [pt. iii 



subject should be undertaken, for the methods of Diamare and Bierry 

 ahke were of questionable reliability. Diamare, however, went rather 

 further into the matter than other investigators, and, thinking that 

 the yolk glucose might only be present there owing to an inflow from 

 the white, examined the ovarian eggs, in which he found glucose in 

 much the same proportion as in the yolks of laid eggs. He does not 

 state whether the ovarian eggs were yellow or white, and, as he 

 frequently gives his results in the form of grams of glucose without 

 mentioning the weight of the fresh material, it is impossible to calcu- 

 late the percentage (see also Tillmans & Philippi) . 



We have already seen that cholesterol was identified in the yolk 

 of the hen's egg by very early workers such as Gobley. In 1908 

 Menozzi and in 191 5 Berg & Angerhausen sho\ved that egg cholesterol 

 was identical with that from milk and bile. It is certainly present 

 in the unincubated yolk both free and in esterified form with fatty 

 acids. Serono and Palozzi investigated a substance from egg-yolk in 

 191 1 which they called "lutein" but which turned out to be nothing 

 but a mixture of cholesterol esters. Other investigators have estimated 

 the amount of free and combined cholesterol in the unincubated egg, 

 and their figures are given in Table 25. 



Table 25. Cholesterol-content of hen^s egg. 



Many Other substances have been found to be present in the egg at the 

 beginning of development, e.g. choline, alcohol, creatine, creatinine, 

 inositogen, lactic acid, plasmalogen (Stepp, Feulgen & Voit, 1927), 

 etc. These will be mentioned as occasion arises during the succeeding 

 sections of the book. Allantoin is not present (Ackroyd). 



The yolk of the hen's egg also contains vitamines, pigments, and 

 a variety of enzymes, but these will be dealt with under their respec- 

 tive sections. As Langworthy has shown, it may also contain very 



