268 THE PHYSIOLOGY OF REPRODUCTION 



One may therefore venture the suggestion that lecithin and its 

 aUies have a similar function with regard to other substances 

 afEecting the life of the cell under normal conditions. Some 

 experiments of the writer,^ carried out in 1908, suggest that 

 these phosphorised fats may act as oxygen-carriers, and that 

 they may thus fulfil an important function in cell-respiration. 

 A similar view has been put forward recently on purely 

 theoretical grounds by Mansfeld.^ 



However that may be, there can be httle doubt that in 

 the egg which contains an exceptionally large amount of phos- 

 phorised fats these substances have to fulfil a different function. 

 Phosphorus enters into the composition of many cell consti- 

 tuents, for instance, the complex protein substances found 

 in the nuclei of cells, the so-called nucleoproteins, so that 

 the assimilation of phosphorus is an important factor in 

 the growth of an organism. Feeding experiments on Man 

 and on animals have made it probable that phosphorus in 

 organic combinations is better assimilated than phosphorus 

 which is given in the form of inorganic phosphates. In birds 

 the yolk of the egg fulfils a function similar to that of the milk 

 in Mammals ; both supply the offspring with the material 

 necessary for its growth. We thus find that both the yolk 

 and the milk are not only rich in phosphorus, but that most of the 

 phosphorus is present in organic combination, as casein and 

 nuclein in the latter, and as vitellin and phosphorised fats in 

 the former. 



We also find that during incubation the vitellin disappears 

 and the phosphorised fats diminish, so that, at the twentieth 

 day, their quantity is reduced by one half.^ It is, of course, 



1 Unpublished observations. It was found that watery emulsions of egg- 

 lecithin absorbed much more oxygen than water alone or watery solutions of 

 proteins, and that such a lecithin-emulsion sometimes greatly accelerated 

 the oxidation of hydriodic acid by the oxygen of the air. The i-esults ob- 

 tained were, however, very variable. 



' Mansfeld, " Narkose und Sauerstoff mangel, " Pfluger's Archiv, vol. oxxix., 

 1909. 



^ Merconitzki, " Die quantitativeu Veranderungen des Lecithins im 

 enstehenden Organismus," Russky Wratsoh, 1907, quoted from Biochemisches 

 Gentralblatt, vol. vi., 1907. Plimmer and Scott, "The Transformations in 

 the Phosphorus Compounds in the Hen's Egg during Development," Jour, of 

 Physiology, vol. xxxvili., 1909. 



