3o6 THE UNFERTILISED EGG AS A [pt. iii 



The figures which have been obtained by those investigators 

 who have examined the iron-content of eggs are seen in Table 29. 

 All found a great deal more iron in the yolk than in the white, 

 as might have been expected from the earlier micro-chemical 

 researches of Tirmann and Kobert. This kind of work had been 

 originated by Schmiechovski, and was continued later by Wasser- 

 mann in the interesting paper already referred to. Schmiechovski 

 found iron histochemically throughout the yolk, but considered that, 

 in the white or milky yolk, it was confined to the megaspheres. 



Table 29* Iron in hen's eggs. 



Italic figures indicate dry weight data. 

 FcaOs gm. % wet weight 



Without iron-rich diet With iron-rich diet 



, ' ^ r ^ ^ 



Egg-white Egg-white 



Egg- plus Egg- plus 



white Yolk yolk Shell white Yolk yolk Shell Investigator and date 



•0024 -0088 -0047 -0272 -0040 'oogs -0059 -0272 Loges & Pingel (1901) 



— — -0046 — — — -0040 — Kreis (1900) 

 •0057 -026 •0165 — — — — ^ Lebbin (1900) 

 ■03 -05 -03 _____ 



•001 12 -00995 '00425 — — — — — Hartung (Mar. 1902) 



•00087 -01106 -00451 — — — — — ,, (May 1902) 



— — — — -00208 -01621 -00729 — ,, (June 1902) 

 Trace -0108 — — — — — — Bunge (1892) 



— -0121 -0018 — — '0175 -0032 — Hofmann (1901) 



— -;r -0057 — — — — — Boussingault (1850) 



— -063 -og§ — — — — — Leveque & von 



Tschermak (191 3) 

 None 'OI43 — — None '0143 — — Elvehjem, Kemmerer, 



Hart, & Halpin (1929) 



Wassermann, using both the ammonium sulphide and the Berlin 

 blue methods, decided that it was present in both kinds of yolk, 

 but that it was not confined to those special elements in the white 

 part. In fact, it was very much more abundant in the white than 

 in the yellow part. This finding has never been corroborated by 

 chemical analysis, but, if it is, it will have considerable importance, 

 in view of the time at which haemoglobin is most vigorously manu- 

 factured by the embryo. For a further discussion of these questions 

 see the section on pigments. 



i-ii. General Characteristics of Non- Avian Eggs 



With this we may conclude the discussion of what is known 

 about the typically terrestrial egg, that of the bird. Now 



