l6l0 HANDBOOK OF PHYSIOLOGY ^CIRCULATION II 



fig. 26. Pattern of distribution of India ink 

 in monkey placenta perfused by way of the 

 aorta. [Permission of Ramsey (183).] 



■> 



interchange is not questioned [Flexner & Gellhorn 

 (80), Hellman et al. (101), see Reynolds (198) for 

 review]. It was shown long ago [Paton et al. (170)] 

 that the volume of amniotic fluid in any species is 

 nearly constant at any given stage of normal preg- 

 nancy [Hammond (94), Reynolds (198), Lell (134), 

 Wislocki (249), McCafferty (146)]. Although some 

 amniotic fluid surely passes from the fetus to the 

 amniotic sac [Reynolds (201)], water passes by an 

 extraplacental route as well [Paul et al. (171)]. More- 

 over, maternal emboli of amniotic fluid detritus are 

 known to occur [Bachman (14)]. Sfameni (219) has 

 reviewed the lymphatic circulation in the vascular 

 relations between the mother and fetus. The theo- 



retical aspects of the subject are reviewed by Plentl 

 (174, 175) and McCance & Dickinson ( 1 47). 



Knowledge of the manner by which maternal 

 blood reaches the placenta has received much study 

 in recent years. Maternal blood reaches the placenta, 

 of course, by endometrial branches of the uterine 

 arteries. Blood is drained from the placenta by endo- 

 metrial branches of the uterine veins. These are 

 largely anatomical studies based upon injection of 

 India ink or other media into the aorta or the femoral 

 vein followed by sections and study of the injected 

 regions [Ramsey (181)]; by injection-corrosion prep- 

 arations; and by serial radiography [cf Ramsey et al. 

 (188)]. Direct injections of uterine vessels of excised 



PRIMARY PLACENTAL''' 



• Totol orteries 7 



SECONDARY PLACENT, 



C-750- I23days 



o Total veins 19 



• Total arteries 10 



o Total veins 18 



fig. 27. Total arterial and venous openings in the placenta of the monkey in Lite pregnancy. 

 [Permission of Ramsey (184).] 



