FCETAL NUTRITION: THE PLACENTA 365 



deny that by such physical processes the non-diffusible sub- 

 stances with large molecules, e.g. haemoglobin and other blood 

 proteins, can be absorbed by the syncytium. They postulate 

 a vital action on the part of the cells, by which the necessary 

 material is selected by the syncytium, and altered to a form 

 in which it may be transmitted to the foetal circulation. It is 

 not yet settled whether the activity of the syncytium is due to a 

 phagocytic power or to an enzyme action. 



There is a third theory regarding the transmission of nutritive 

 material . from the mother to the foetus, viz. by the actual 

 passage of maternal leucocytes, charged with nutriment, from 

 the one circulation to the other. This theory was first ad- 

 vocated by Rauber ^ as the result of microscopic investigations, 

 and he instanced, as further evidence in its favour, the greater 

 number of leucocytes in the blood of the umbiHcal vein than 

 in that of the artery. This view, which explained satisfactorily 

 the passage of non-diffusible materials, subsequently received 

 wide support. Thus Wiener ^ said : " It may be held as nearly 

 without doubt that leucocytes cross from the maternal to the 

 foetal blood," and Preyer ^ considered the passage of leucocytes 

 " indisputable." The first objection was raised in a paper by 

 Paterson.* In "it he recorded three cases of pregnancy com- 

 phcated by leucocythaemia in the mother, and stated that the 

 infants appeared quite normal and healthy, and their blood 

 was of the usual colour and not white hke the mothers'. These 

 results were corroborated in similar cases by Cameron ^ and 

 Sanger,' who actually counted the foetal leucocytes and found 

 no increase. These observations, and the inabihty of subse- 

 quent investigators to demonstrate healthy leucocytes in the 

 tissues intervening between the maternal and foetal blood, 

 have led to the abandonment of Rauber 's theory. 



' Rauber, Veber den XJrsprung der Milch und die Emahrung der Frucht 

 im aligemeinen, Leipzig, 1879. Also Zool. Anz., No. 70. 



' Wiener, "Die Ernahrung des Fotus," Samml. Klin. Vortrdge, No. 290. 



' Preyer, Specielle Physiologie dea Embryo, 1883. 



» Paterson, " Cases of Acute Leucocythaemia in connection with Preg- 

 nancy," Edinburgh Med. Jour. , 1870. 



^ Cameron, " The Influence of Leucsemia upon Pregnancy," Intemat. Jour, 

 of the Med. Sc, 1888. 



* Sanger, " Ueber Lenkamie bei Sohwangeren und angeborene Leukamie," 

 Arch.f. Qynak,, vol. xxxiii., 1888. 



