548 ^THE PHYSIOLOGY OF REPRODUCTION 



Peters in an early human ovum.^ But in all placentae yet investigated, 

 iron-containing granules have been observed in the trophoblast. The 

 ;possible sources are hsemoglobin, which is in part absorbed as such 

 by the trophoblast in man (Bonnet ^), nucleoprotein, and the reserve 

 iron of the mother. Nuclein is the only iron-containing constituent 

 of yolk of egg, and must serve for the manufacture of haemoglobin 

 in the de^reloping chick. It is also known that in the adult organism 

 nucleoprotein is a better source of iron for hsemoglobin than any 

 inorganic or other organic compound hitherto administered by the 

 mouth.^ Hence it is not difficult to conceive that the same process 

 may occur in the foetus. But whether it is the food nucleoproteins 

 or the organised nuclein bodies of the maternal organism that are 

 utilised, is unknown.* With regard to the reserve iron of the 

 mother, it is stated by Charrin^ that the store in the spleen is 

 reduced during pregnancy. 



In the foetus iron is required for the synthesis of haemoglobin 

 (see p. 505) and nucleoproteins.® But large amounts of iron are also 

 stored .in the liver and other organs of the embryo without being 

 used immediately. According to Bunge's ^ law, this forms a reserve 

 which is drawn on after birth to make up for the deficiency of the 

 iron in the milk. Thus the liver of a rabbit contains 18 mg. of iron 

 per 100 gm. body- weight at birth, and only 3'2 mg. twenty-four days 

 later. This fact is of great practical importance in the nutrition of 

 infants. The period during which milk is an adequate diet for the 

 infant is limited by the reserve of iron which the infant has stored 

 away in its body before birth. This reserve is sufficient to last during 

 the normal period of lactation. Then a mixed diet, containing food 

 richer in iron than milk, is required. If the mother during pregnancy 

 is kept on a diet rich in iron, the embryo will store more iron than 

 when the diet is poor in iron. If the supply of iron to the mother is 

 kept low during repeated pregnancies abortion may occur.** 



1 See Chapter X., p. 505. 



2 Ibid. 



3 V. Noorden, loc. cit., vol. i., p. 78. 



* As the purine bases of the urine are stated to be decreased in pregnancy, 

 the maternal nucleins are probably not a source of iron for the foetus to any 

 appreciable extent. 



s Charrin, " Physiologie pathologique de la grossesse,'' Gompt. Rend. Soc. de 

 Biol, 1899. 



* The nucleoproteins of the foetal placenta in the sheep differ in their 

 chemical constitution from those of the maternal placental They are probably 

 synthesised in the ovum from lower.complexes, in the same way as the nucleo- 

 proteins of the chick embryo are built up though the egg contains no 

 purine bases. 



' Bunge, "Weitere Untersuchungen uber die Aufnahme des Eisens in den 

 •Organismus des Sauglings," Zdtsch.f.<phynol. Chem., vols. xvi. and xvii., 1892-93. 

 ^ Fetzer, " Experimentelle Untersuchungen iiber den Eisenstoffwechsel," 

 26 Kongressf. inn. Medizin, 1909. 



