THE SOURCE OF THE AMNIOTIC AND ALLANTOIC FLUIDS IN MAMMALS. 73 



round to the maternal mucosa by primitive chorionic villi, at the end of the third 

 month of pregnancy the connection between chorion and mucosa breaks down as the 

 placenta forms, and in all later stages is loose and non-vascular, except at the placental 

 site. The connection between the outer layer of the amnion and the inner layer of the 

 chorion is also loose, and can be readily separated even at full time. 



Viewing the question from the anatomical standpoint, it is difficult to see how the 

 fluids in these vesicles can be derived from the maternal blood. 



2. Pathological Evidence. 



This has been chiefly derived from the study of polyhydramnios and oligohydramnios 

 in the human ovum. The most noteworthy of the recent observations on this subject 

 is Silberstein's (Arch. f. Gfyn., lxviii. 607, 1903). From a study of a 5^-months 

 uni-ovular twin pregnancy, in which one of the sacs contained 6^ litres of fluid, while 

 the other contained very little, he comes to the conclusion that part at least of the 

 human liquor amnii is derived from the foetal kidneys. In the sac containing the 

 large quantity of fluid the foetus was much larger than the other — 783 grms. as 

 contrasted with 488 grms. The heart of the polyhydramniotic foetus was 7 '5 grms., 

 and that of the oligohydramniotic one, 3 grms. ; the kidneys, 2 '9 grms. each, as against 

 1 grm. each; and the bladder, 2'1 grms., as compared with 2 grms. The glomenuli 

 in the kidneys of the larger foetus had a diameter of 97 to 115 micros, while 

 those of the smaller were only from 65 to 66 micros. 



He concludes that, owing to the arrangement of the vascular areas of the two 

 foetuses in the common placenta, the larger foetus had an extra supply of blood, 

 part of which was directly diverted from the smaller one, and that as a result all 

 the organs had hypertrophied, probably beginning with the heart. He considers the 

 excess of liquor amnii in the sac as due to the consequent increased activity of the 

 kidneys. 



The mere fact of only one of the twin amniotic sacs having an excess of fluid is, of 

 course, strong presumptive evidence of the foetal origin of that fluid ; but the evidence 

 afforded that the fluid was secreted by the foetal kidneys is not so convincing. Cases 

 of hydramnios have been recorded in which there has been obstruction in the urethra 

 and hydronephrosis in the foetus (Jaggard, Am. Jour. Oust., xxix. p. 432, 1894). Like 

 conditions in the foetus have been found associated with oligohydramnios, as in cases 

 recorded by Ballantyne (Ed. Med. Jour., xl. 858, 1895) and Blackwood (Ed. Med. 

 Jour., xli. 919, 1896); so that no definite conclusion, either in favour of or against the 

 renal origin of the fluid, can be drawn. 



In other cases the hydramnios has been found associated with conditions interfering 

 with the circulation in the umbilical cord, such as excessive torsion, thrombosis of the 

 vein, and cirrhosis of the liver (Opitz, Central, f. Gi/n., 1898, p. 553). It is well 

 known that hydramnios is often associated with malformations in the foetus, such as 



