466 THE PHYSIOLOGY OF REPRODUCTION 



subcutaneously into pregnant rabbits and guinea-pigs, was carried 

 out to supplement the research upon the ferments. The evidence 

 obtained, according to Frank, favoured the view that the placenta 

 is a passive organ of exchange rather than an active organ of 

 metabolism. The uterus was found to take the stain first; next 

 the yolk membrane, and last the placenta. The kidney and liver 

 in the foetuses readily absorbed the dye but other organs were 

 affected. Goldmann 1 has also investigated the effects of vital 

 staining and traced the paths by which the dye (trypan or pyrrol 

 blue) enters the foetus, and has made a careful study of the behaviour 

 of the placenta towards vital stains. Of especial interest is the 

 marked reaction of the wandering connective tissue cells ("pyrrol 

 cells ") to the vital stain. 



Wislocki 2 found that when trypan or pyrrol blue are injected 

 intravenously into the pregnant rabbit, as with the guinea-pig, mouse, 

 and rat, traces of the colloid may pass into the amniotic fluid, and 

 even stain the foetus. In the case of the cat, however, they only 

 reach the placenta and are stored in the form of granules in the 

 chorionic ectoderm. Wislocki concludes, therefore, that the placenta 

 of the carnivore is less permeable than that of the rodent. Colloidal 

 dyes injected into the amniotic cavity of the cat and guinea-pig 

 in later pregnancy are absorbed through the gastro-mteatinal and 

 respiratory tracts and by diffusion through the amniotic membrane. 

 The foetus becomes vitally stained, but none of the colloidal material 

 passes into the maternal circulation. Wislocki also administered 

 intravenously a solution of India ink to pregnant rabbits and other 

 animals, and found that neither the chorionic epithelium nor the 

 placental endothelium could absorb or phagocytise granules as coarse 

 as this, and the placental and foetal membranes were entirely un- 

 stained. Phenolsulpho-naphthalein injected into the foetal peritoneal 

 cavity is absorbed by the blood-stream, passes to the placenta, 

 and thence to the maternal circulation and kidneys; it is also 

 excreted by the foetal kidneys. Trypan blue (a less diffusible colloid), 

 when similarly injected, vitally stains the foetus, is excreted by the 



1 Goldmann, "Neue Untersuchungen iiber iiussere und innere Sekretion 

 des Gesunden und Kranken Organismus im Lichte der 'Vitalen Farbung,'" 

 Tubingen, 1912 ; repriri*ted from Beiti\ zur klin. Chir., vol. Ixxviii., 1912. 

 This memoir, which contains many references to literature, includes also a 

 detailed account of the investigation of the glycogen, fat, iron, and haemoglobin 

 absorption through the placenta by microchemical methods. The methods of 

 vital staining have been taken advantage of in their application to the study 

 of the cell nucleus by Kite and Chambers (" Vital Staining of the Chromosomes 

 and the Function and Structure of the Nucleus," Science, vol. xxxvi., (November) 

 1912. 



2 Wislocki, "Experimental Studies on Fetal Absorption," I. to IV., Contri- 

 butions to Embryology, vols. xi. and xiii., Carnegie Institute (Washington) 

 Publication 276, 1920-21. See also Johns Hopkins Hospital Bull., vol. xxxii., 

 1921 ; and Anat. Rec., vol. xxi., 1921. 



