74 D. NOEL PATON, B. P. WATSON, AND J. KERR ON 



spina bifida, auencephaly, etc. But which is the primary condition has never been 

 definitely ascertained. Altogether, very little light has been thrown upon the origin 

 of the fluids from a study of pathological conditions in the human subject. 



3. Experimental Evidence. 



(1) The Removal of the Fluids. — It seemed to us that the effects of withdrawing 

 the fluids might throw light upon the question of their origin, and one of us carried out 

 a series of experiments on rabbits (Watson, Jour, of Obstet. and Gyn. of the British 

 Empire, Jan. 1906). The fluids were withdrawn from the uterus by an aspirator 

 needle (the abdomen having been opened) at different periods of pregnancy. In the 

 early stages of pregnancy, the fluid removed was yolk-sac fluid, and in the middle and 

 later stages liquor amnii. In both cases the withdrawal resulted in immediate death of 

 the foetus, and this was followed by a degeneration of the foetal part of the placenta. 

 The maternal part of the placenta, on the other hand, continued to grow and to undergo 

 the various histological changes which occur under normal circumstances. In no case, 

 however, was there any re-formation of the liquor amnii. This would appear to indicate 

 that in the rabbit the fluid must be foetal in origin, since its secretion is arrested by the 

 death of the foetus, in spite of the fact that the foetal part of the placenta does not show 

 marked signs of degeneration for a few days, and the maternal part remains apparently 

 normal up to the time it is cast off. 



(2) The Passage of Chemical Substances from the Mother to the Fluids. — A large 

 number of experiments have been recorded showing that chemical substances injected 

 into the maternal circulation may appear in the fluids ; and from certain of these the 

 conclusion has been drawn that the fluids are formed directly from the maternal blood. 

 The best known of these are by Zuntz {Pflilg. Arch., Bd. xvi. p. 548, 1878). 



The method he employed was that which had been already used by Gusserow in 

 his classical investigations {Arch. f. Gyn., Bd. iii. p. 241, 1872), and according to 

 Gusserow by even earlier observers, e.g. Meyer (Bischoffs Entwickelungsgeschichte, 

 p. 515). The substance used by Zuntz was sodium sulphindigotate, which he injected in 

 large quantities into the veins of pregnant rabbits. He states that the amniotic fluid 

 was coloured blue, while the kidneys and other tissues of the foetus were free of the 

 pigment, and that, when he killed the foetus by injecting into it through the uterine 

 wall caustic potash before injecting the pigment, in one experiment at least the pigment 

 was detected in the fluid. 



These observations were confirmed by Wiener for rabbits in the later stage of 

 pregnancy {A rch. f. Gyn., Bd. xvii. p. 24, 1881, and Bd. xxiii. p. 183, 1884). He further 

 showed that the passage of pigment into the foetal fluids was more rapid when the 

 kidneys of the mother were first removed. In two pregnant dogs he entirely failed to 

 find the pigment in the foetal fluids, and he also failed in rabbits during the early stages 

 of pregnancy. 



