THE SOURCE OF THE AMNIOTIC AND ALLANTOIC FLUIDS IN MAMMALS. 81 



of iodides in the fluids and in the foetal urine after their injection into two pregnant 

 cows and one pregnant goat. In the two cows he finds the iodide in greater percentage 

 amount in the amniotic fluid than in the urine ; while in the goat he finds it in 

 about the same amount in the amniotic, but to a less amount in the allantoic than 

 in the blood of the foetus. 



The very consistent results which we obtained with a series of chemical substances, 

 in our opinion, counterbalances the value of these two observations, especially as the 

 method employed by us in the determination of the amount of iodine present is more 

 satisfactory than that used by Copper. 



But Copper does not attempt to argue in favour of the direct passage of the iodide 

 from the maternal blood, but he believes that it passes through the maternal placenta to 

 the chorionic villi of the foetal placenta, and that from the efferent vessels of this it is 

 carried into the wall of the allantoic vesicle, which surrounds the amnion, and that from 

 there it passes into the fluids. 



Gusserow (Arch. f. Gyn., Bd. iii. p. 241, 1872) had already indicated the possible 

 importance of the vessels running over the placenta. 



Copper has repeated upon ruminants the experiments previously performed by 

 ToERNGREN(C.i£. Soc. biol., 1888, p. 543) on rabbits, of injecting iodides into the amniotic 

 sac and recovering them in the maternal urine. Such observations seem to prove no 

 more than that iodides are taken up by the blood-vessels in the walls of the allantois 

 and so carried to the placenta to be passed into the maternal circulation. They do not 

 in any way indicate that these fluids are formed from the maternal blood-vessels. # 



2. The Mode of Production of the Fluids by the Foetus. 



It having been shown that the fluids and their constituents are foetal in origin, 

 the question of how they are produced has next to be considered. 



(1) They may be produced as a transudation from the blood-vessels coursing in 

 the walls of the vesicles, which, as has been indicated, are purely foetal in nature. 



(2) They may be derived from the kidneys of the foetus. 



(3) They may be derived from both these sources. 



(4) One fluid may be formed from the other to a greater or less extent, or 

 each may derive constituents from the other by diffusion or osmosis through the 

 amniotic and allantoic membranes which separate them. 



The question of the parts played by (1) transudation from the blood-vessels of the 

 allantois and (2) by the action of the foetal kidneys may first be considered. 



It must be at once admitted that the small amount of fluid which is included in 

 the amniotic sac at the time of its development must have an origin independent of 

 blood-vessels and kidneys, and must be derived from a breaking-down or secretory 



* Copper gives a very excellent summary of the previous work on the subject. 



