158 



And in conclusion a few words may be said on the iron gran- 

 ules described above as being found in certain subepithelial cells, 

 especially at the root of the mesometrium. These granules dis- 

 appear, as pregnancy advances, in the placental regions, and appear 

 therefore to be used in the nutrition of the embryo; but exactly 

 how, I cannot say. I thought at one time that the iron might 

 be taken up, and secreted by the glands; but have failed to ob- 

 tain any iron reaction in the coagalum in the lumina of the 

 glands (I have since seen in Tupaia iron granules in the epithe- 

 lium of the glands). It is at any rate quite clear, that since, as 

 is well known, an enormous quantity of iron is stored up in the 

 liver of' the embryo, which is used by it during lactation, this 

 iron must be derived during pregnancy from the niother; part of 

 it probably comes from the iron granules, part also from the 

 ingestion of red blood corpuscles by the trophoblast, and in this 

 connection it is important to remember the formation of bili- 

 verdin in the bordure verte of the carnivora and in the yolk-sac 

 of the shrew. 



But it remains for future investigations to shew what relation 

 there is, if any, between this destruction of red blood corpuscles 

 and absorption of iron compounds by the embryonic tissues, and 

 the diminution and possibly re-formation of haemoglobin in the 

 maternal organism, perhaps even in the placenta itself, during 

 the progress of gestation. 



PART II. 



CRITIQTJE OF PREVIOUS WORK, TOGETHER WITH SOME REMARKS 

 ON THE COMPARATIVE ANATOMY OF THE PLACENTA. 



Our knowledge of the minute anatomy of the placenta of the 

 so-called 'deciduate' Eutheria is only of comparatively recent 

 growth; it may be said to have begun with the almost simulta- 

 neous publication by Duval and ïïubrecht of their memoirs on 

 the placentation of the Rabbit and the Hedgehog. Since then a 



