298 



THE UNFERTILISED EGG AS A 



[PT. Ill 



Again, during the fat feeding, tiie saponification value of the egg- 

 fat was 176 (166-190) and during the rest of the time 173. The iodine 

 value was in the former case 70-5 and in the latter 70-8. 



Table 24. Lipoid in egg-yolk. 



Lecithin 



Thrush 

 Cat ... 

 Rabbit 

 Guinea-pig 



Lecithin in % dry 

 weight at birth or hatching 

 8-18 

 5-06 

 4-91 

 3-79 



Some suggestive investigations on the biological significance of 

 ovolecithin were made b-y Glikin in 1 908, whose figures are shown in 

 Table 24. Choosing the pigeon as a typically nidicolous bird, and 

 the hen as a typically nidifugous one, he was able to show, using a 

 variety of extraction methods, that the yolk of the former was con- 

 siderably richer in lecithin than the latter, the former containing 

 about 29 per cent, dry weight, and the latter about 17. The further 

 but rather fragmentary observations which he made on the starling 

 and the turtledove confirmed this relationship. It is interesting that 

 Tso informs us that certain small Chinese breeds of hen produce very 

 small eggs (scarcely 40 gm.) and that these contain a much higher per- 

 centage of lipoids than ordinary eggs though an equivalent percentage 

 of protein. He concluded that lecithin, one of the most essential 

 yolk-constituents, was specially concentrated in nidicolous yolks and 



