FCETAL NUTRITION: THE PLACENTA 359 



researches of Goodsir. 1 He first studied the placental cells with 

 regard to their function. His predecessors had spoken in the 

 vaguest terms of the passage of nutriment from mother to foetus, 

 but Goodsir had definite ideas. He described the villi as having 

 two covering layers of cells, an external system belonging to the 

 decidua, and an internal belonging to the chorion. As to their 

 function, he says : " The external cells separate from the blood 

 of the mother the matter destined for the blood of the foetus, they 

 are secreting ; the internal cells absorb the matter secreted by 

 the agency of the external cells." Thus we have the active part 

 of placental metabolism referred for the first time to the cells of 

 the villi. 



The importance of the intervillous spaces for fcetal nutrition 

 was first emphasised by Weber, 2 and they were the subject of 

 close attention. The Hunterian doctrine that in the human 

 placenta they contained blood was not yet established, and 

 their mode of development gave rise to a long-continued con- 

 troversy. John Hunter considered them outwith the maternal 

 vascular system, and his view was supported by Owen, 3 Kolliker, 4 

 and Farre. 5 Weber and Reid 6 held that the spaces were 

 bounded by a thin maternal membrane, and Goodsir described 

 two layers of maternal tissue between the blood in the sinuses 

 and the vessels of the villi. 



The investigation of the intervillous spaces and the 

 epithelial investment of the villi was carried on by Turner, 

 Ercolani, Langhans, and many others. Turner 7 and Waldeyer 

 looked on the intervillous spaces as dilated maternal capillaries ; 

 but while Turner held that the villi, at least in part, pene- 

 trated their endothelium, Waldeyer supposed that they pushed 

 the endothelium before them, and so got a covering of this 



1 Goodsir, Anatomical and Pathological Observations, Edinburgh, 1845. 



2 See Wagner's Elements of Physiology, translated by Willis, London, 

 1841. 



3 See Note in John Hunter's Collected Works, Edit, by Palmer, vol. iV. 



4 Kolliker, Entvncklungsgeschichte, 1861, 1884, &c. 



5 See Tod's Cyclop axlia, Article " Uterus," 1858. 



6 Reid, " On the Anatomical Relations of the Blood- Vessels of the Mother 

 to those of the Foetus in the Human Species," Edinburgh Medical and 

 Surgical Journal, vol. lv., 1841. 



7 Turner, "Some General Observations on the Placenta," &c. , Journal of 

 Anatomy and Physiology, vol. xi., 1877. 



