FCETAL NUTRITION: THE PLACENTA 395 



the active part of placental metabolism referred for the first time to 

 the cells of the villi. 



The importance of the intervillous spaces for foetal nutrition was 

 first emphasised by Weber,! and they were the subject of close 

 attention.-, TheHunterian doctrine that in the human placenta they 

 contained blood was not yet established, and their mode of development 

 gave rise to a long-continued controversy. John Hunter considered 

 them outwith the maternal vascular system, and his view ' was 

 supported by Owen,^ KoUiker,^ and Farre.* Weber and Eeid^ 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* and Waldeyer looked on the intervillous 

 spaces as dilated maternal capillaries; but while Turner held that 

 the villi, at least in part, penetrated their endothelium, Waldeyer 

 supposed that they pushed the endothelium before them, and so got 

 a covering of this maternal layer. Langhans '' regarded the spaces as 

 formed by that part of the lumen of the uterus which lay between 

 the surface of the mucosa and the chorion, and thought that the villi 

 by eroding vessels came to be bathed in extravasations of maternal 

 blood. Klebs^ considered them to be lymph-spaces, and therefore 

 extra-vascular; and Jassinsky^ described them as being formed by 

 the penetration of the villi into the maternal glands, whose epithelium 

 came to clothe the villi externally. Now it has been proved from 

 the examination of early ova that the intervillous spaces are entirely 

 foetal and are formed in the epiblast. 



The investigations of Langhans proved to be the turning-point 

 in the controversy regarding the investment of the villi. He showed 

 that it consisted in the earlier stages of pregnancy of a double 

 covering, a deep layer of cells (Langhans' layer), and superficially a 

 mass of " canalised fibrin." The presence of fibrin had been noted 



' See Wagner's Elements of Physiology, translated by Willis," London, 1841. 

 2 See note in John Hunter's Collected Works, Edit, by Palmer, vol. iv. 

 ' Kolliker, Entwioklung*geschichte, 1861, 1884, etc. 



* See Tod's Cyclopaedia, Article " Uterus," 1858. 



^ 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. Iv., 1841. 



* Turner, "Some General Observations on the Placenta, etc.," Jour, of Anat- 

 and Phys., vol. xi., 1877. 



' Langhans, " Untersunhungen iiber die menschliche Placenta," Arch, f 

 Anat. u. Phys., Anat. Abth., 1877. 



8 Klebs (E.), "Zur vergleichende Anatomie der Placenta," Arch. f. mikr, 

 Anat., vol. xxxvii., 1891. 



' Jassinsky, "Zur Lehre iiber die Struktur der Placenta,'' Virchow's Arch.^ 

 vol. xl., 1867. 



