272 



THE UNFERTILISED EGG AS A 



[PT. Ill 



physical and colloidal rather than to chemical differences, and the 

 whole question should be reinvestigated. There seemed to be no 

 special significance in the distribution of the ovomucoid which was 

 precipitable by percaglobulin ; thus it was present in the accipitres, 

 grallae, lamellirostres, longipennes and pygopodes, but not in the 

 passeres, zygodactyli, pullastrae and steganopodes. As for the fowls, 

 it was present in the eggs of the hen and pheasant, but not in 

 those of the guinea-fowl. Morner was inclined to agree with Milesi's 

 view that ovomucoid did not exist as such in the natural egg-white 

 at all. 



Table 14. Variations in properties of avian egg-white. 



As has already been observed, Sir Thomas Browne was one of 

 the first to note that the coagulated egg-white of the gull's egg was 

 quite different in consistency and translucency from that of the hen's 

 egg. In 1863 Davy collected some data on these points, which are 

 shown in Table 14, and Tarchanov devoted much time to the 

 question in the 'eighties of the last century. He found that the whites 

 of many kinds of eggs would not coagulate in the ordinary way on 

 boiling, but either remained liquid and transparent or else set to a 

 watery translucent jelly. This he called " tataeiweiss ", and as he went 

 on to examine the distribution of this property he found that it was 

 associated with the hatching quality of the bird in question. Thus 

 all nidifugous birds, whose chicks are born fully feathered ("downy") 

 and soon leave the nest, had eggs with ordinary egg-white, but all 

 nidicolous ones, whose chicks are hatched as "squabs" or naked and 

 weak, and have some development yet to complete, had eggs with 

 uncoagulable or transparent egg-white. Thus the sand-martin, linnet, 

 finch, thrush, canary, crow, dove, rook, nightingale, robin, starling 

 (roughly passeres and pullastrae), all had tataeiweiss] while the hen, 



