54 EXPERIMENTAL STUDIES ON FETAL ABSORPTION. 



II. BEHAVIOR OF THE FETAL MEMBRANES AND PLACENTA OF THE CAT 

 TOWARD COLLOIDAL DYES INJECTED INTO MATERNAL BLOOD-STREAM. 



The extensive researches of Gusserow, Fehling, Zuntz, Zweifel, Wiener, 

 Benecke, Krukenberg, and Preyer have demonstrated the passage of gases and 

 dissolved crystalline substances from the maternal into the fetal circulation. 

 Traces of potassium iodide, potassium ferrocyanide, sodium salicylate, benzoic acid, 

 sodium indigo sulphonate, etc., were observed in the fetal urine and in the amniotic 

 fluid after their administration to the mother. The passage of chloroform from the 

 maternal to the fetal circulation has been observed repeatedly. That true solutions 

 are capable also of passing in the opposite direction, from fetus to mother, has been 

 shown for strychnine by Savory and later by Gusserow; for nicotin and curarine 

 by Preyer, for alcohol by Nicloux. 



For many years there was less clarity concerning the passage of formed sub- 

 stances (such as proteins and fats) through the placenta. It is now believed, 

 mainly from the experimental work of Ascoli, Bonnet, Hofbauer, and Goldmann, 

 that such substances are not directly transmitted through the placenta, but must 

 first undergo a breaking-down in the epithelium of the chorion before assimilation by 

 the fetal blood-stream is possible. Hofbauer considers the activity of the chorionic 

 epithelium as comparable in many respects to absorption by the intestinal mucosa. 

 A number of observations have been made on the behavior of the fetus toward 

 inert colloids and particulate matter introduced experimentally into the maternal 

 blood-stream. The general conclusion drawn from them is that foreign colloidal or 

 particulate matter fails to reach the fetal circulation, due to the fact that the 

 placenta and fetal membranes are impenetrable to colloidal substances which the 

 chorionic epithelium is unable to convert into an assimilable form. 



Jassinsky (1867) injected a suspension of carmine into pregnant dogs and, 

 although the animals died from this procedure in about 20 minutes, he observed 

 that the substance did not reach the fetal circulation but was held up in the placenta. 

 Reitz (1868) injected a suspension of cinnabar into the jugular vein of a 

 pregnant rabbit. He claims to have subsequently found particles of the injected 

 material in the coagulated blood of the heart and in the capillaries of the brain of 

 the fetus. His observations appear erroneous in the light of our present knowledge. 

 Hoffmann and Langerhans (1869) state that after injecting a nearly full-term 

 rabbit with carmine they found no trace of the dye in the fetus or placenta. 



Fehling (1876) injected india ink into the femoral vein of a pregnant rabbit 

 and killed the animal 24 hours later. He observed that the fetus contained none 

 of the ink, but he does not describe how the placenta prevented it from entering 

 the fetal blood-stream. 



Schlecht (1907) describes a pregnant mouse winch had been stained by the 

 repeated injection of lithium carmine. The dye had failed to stain the fetuses but 

 was plainly visible in the placenta and fetal membranes. Microscopically it was 

 found throughout the placenta in the form of fine red granules in the cytoplasm of 

 the chorionic epithelium. None of the decidual cells contained dye granules. The 

 outermost membrane of the mouse (the inverted yolk-sac, which Schlecht wrongly 



