FCETAL NUTRITION: THE PLACENTA 407 



this pigment in alcoholic extracts of the placenta. He found 

 two other pigments, one absorbing a small part of the violet end 

 of the spectrum, and the other showing two absorption bands, 

 which differed slightly from those of oxyhaemoglobin in neutral 

 solution and of hsematoporphyrin in acid solution. This pig- 

 ment is obviously a haemoglobin derivative, and from it bilirubin 

 may be formed. It is present in the sheep and cow during 

 pregnancy, but not in the virgin uterus of the sheep. A similar 

 yellowish-brown pigment occurs in the crypts and the tissues 

 outside them, and also, according to Assheton, in the maternal 

 blood-stream. It is not yet possible to explain the exact 

 significance of these changes. The iron-free pigment is appa- 

 rently a waste product, and the iron-containing part is stored in 

 the fetal organs. Whether the foetus subsequently synthesises 

 part of the organic iron compound into haemoglobin, or absorbs 

 minute quantities of haemoglobin as such, according to its re- 

 quirements, is unknown. 



The cotyledonary and inter-cotyledonary parts of the placenta 

 present differences both anatomically and physiologically. In 

 the inter-cotyledonary region are the glands, and here only are 

 found the gland-secretion and the " cellular " secretion. In 

 the cotyledonary parts the glands are absent. Here the villi 

 are formed, and they effect an attachment to the mucosa by the 

 greater activity of the trophoblast. Assheton has suggested 

 that this hyper-activity may be stimulated by the absence of 

 glands and consequently of uterine milk in the cotyledons, the 

 fetal ectoderm attacking the mucous membrane more vigorously 

 in order to obtain food. The blood effusions are also cotyle- 

 donary, and the eosin and iron reactions are obtainable in the 

 adjacent trophoblast, and not at other places. Finally, it is 

 probable that the exchange of oxygen and carbonic dioxide is 

 carried out in the cotyledons. Here the maternal capillaries 

 are more dilated than outside the burrs, anji they come close 

 up to the surface, some of them even impinging on the lining 

 membrane of the crypts. Between them and the allantoic 

 vessels in the villi intervene only a small amount of mesoblast, 

 the cellular trophoblast, and the lining of the crypts which, 

 according to Assheton, corresponds to the plasmodiblast of the 

 bat. In the inter-cotyledonary regions, on the other hand, the 



