SECT, i] PHYSICO-CHEMICAL SYSTEM 299 



was associated with the property of early hatching or birth. Thus 

 he compared the thrush (nidicolous) with the guinea-pig, which is 

 born almost ready to eat green food and hardly passes through a 

 lactation stage; in the body of the former 8 gm. per cent, lecithin dry 

 weight was found, in the latter only 4. The new-born cat and rabbit 

 occupied intermediate positions. It is interesting to note that Glikin's 

 figures bear out those of Tarchanov on the question of water-content 

 of yolks from the two types of birds. 



Tornani affirmed in 1909 that a difference in lecithin-content was 

 observable between fertilised and unfertilised eggs. But as he gave 

 no figures in support of his contention, it has not been treated with 

 much respect by subsequent workers. 



The carbohydrate of the yolk has been the subject of only a very 

 few researches compared with that of the white. The figures which 

 have been obtained are shown in Table 16, and it will be seen that 

 in no case has the total carbohydrate been estimated, and only 

 in one case the glycogen. After Claude Bernard's isolation of gly- 

 cogen from the yolk, a persistent belief grew up that considerable 

 amounts of this substance were present there ; this was apparently 

 based on the description by Dareste in 1879 of "amyloid bodies" in 

 the yolk which gave microchemically a strong blue colour with 

 iodine. Dastre immediately pointed out that the occurrence of starch 

 there was highly improbable, and that if any glycogen was there it 

 should give a wine-red colour; he himself, however, could find 

 neither. But he did not succeed in suppressing the rumour, for 

 Virchow, and later Schenk, supported Dareste, though nothing has 

 been heard of this yolk-constituent since 1897, and Sakuragi's 

 analysis revealed the presence of only 2-2 mgm. per cent, of glycogen. 

 Bierry, Hazard & Ranc asserted in 191 2 that they could obtain a 

 great increase of carbohydrate after hydrolysing the yolk with 

 hydrofluoric acid under pressure, but this would not imply, as they 

 seemed to think, that glycogen was present, for all kinds of other 

 compounds such as proteins (Gross' protein for instance) might yield 

 glucosamine under such treatment. They identified glucosamine in 

 the hydrolysate. On the other hand, Diamare, who hydrolysed with 

 acetic acid, could only obtain faint traces of combined glucose in 

 the yolk. He dialysed both white and yolk, and in both cases was 

 able to estimate the free sugar, but in the case of the yolk very little 

 combined glucose seemed to be present. Further studies on this 



