THE SOURCE OF THE AMNIOTIC AND ALLANTOIC FLUIDS IN MAMMALS. 75 



It was thus in rabbits only that the passage of this colouring-matter to the fetal 

 fluids, without its presence having been detected in the foetus, was observed by these 

 investigators. 



Krukenberg (Arch. f Gyn., Bd. xxii. p. 39, 1884) criticises their conclusions, 

 pointing out that the recognition of sulphindigotate of soda in tissues is not easy, as 

 was indicated by Heidenhain (Schultzes Arch., Bd. x. p. 35), who stated that, by 

 injecting very small quantities, the urine may be made distinctly blue, while it is 

 impossible to recognise the blue colour in the tissues. Krukenberg has repeated 

 this experiment on the rabbit, and finds that, while the urine is distinctly blue, it is 

 impossible to detect the pigment in the kidneys and liver. He does not prosecute 

 the question of whether this is simply due to the small quantity of pigment, or 

 whether "organic substances in close contact with small quantities of the pigment 

 can decolorise it." 



He further criticises the experimentum crucis of killing the foetus by injecting caustic 

 potash and then finding a slight blue coloration of the amniotic fluid. Certainly it 

 seems possible that a traumatic communication might thus have been established 

 between the maternal vessels and the fluids — a conclusion which is supported by the fact 

 that in all experiments but one the red coloration of the fluid from extra vasated blood 

 prevented the detection of the blue pigment. 



Opposed to the conclusion of Zuntz and Wiener are the experiments of Gusserow 

 of injecting benzoic acid into the maternal blood and finding hippuric acid in the 

 fcetal fluids. Accepting the conclusion of Bunge and Smiedeberg that the synthesis of 

 this substance takes place in the kidney, this observation favours the view that the fluids 

 are produced from the embryonic kidney. 



II. Present Investigations. 



The unsatisfactory state of our knowledge as to the source of these fluids induced us 

 to take up the question, and we have studied it by two different methods — first, by a 

 continuation of the method of Gusserow, Zuntz, and others ; and secondly, by a study of 

 the chemistry of the fluids. 



1. The Part played by the Foetus in the Passage of Substances from the Maternal 



Circulation to the Fluids. 



The objections to the use of the blue sodium sulphindigotate appeared to us so 

 considerable that we have selected another pigment which is extremely easy to recognise 

 in the smallest quantities, namely, fluorescin. We have also made experiments with 

 three substances which are easily recognised by their colour reaction — sodium iodide, 

 sodium ferrocyanide, and sodium salicylate. 



For these experiments we have used the rabbit, guinea-pig, cat, and dog. The two 



