NOURISHMENT OF THE FCETUS. 22f 



up the evolution of the foetus, by its contact, the spongy cake takes 

 up from the womb the elements of reparation, and operates on them, 

 forming a fluid more or less analogous to blood, which is then ab- 

 sorbed by the radicles of the umbilical vein. The placenta absorbs 

 in the uterus, so as to form the fluids of the fogfus, as the liver, the 

 kidney, the seminal gland, Sic, take up from their own vessels the 

 materials from which to form the bile, the urine the prolific liquor, 

 &c.; as trees and plants absorb from the ground the principles of the 

 numerous compounds they contain: and I see nothing in all these 

 actions very difiicult of comprehension. 



§. n. Circulation of the Fcetus. 



Whatever may be the manner in which blood or other fluids reach 

 the placenta, it is, notwithstanding, necessary for them afterwards 

 to traverse the various organs of the foetus for their noUlishment ; 

 however, their circulation does not in all respects resemble that 

 which takes place after the birth of the child. 



567. In the adult, the septum that divides the two auricles of the • 

 heart is complete, and separates them from each other perfectly; in ' 

 the fcetus, on the contrary, this septum has an opening through it, 

 called {he foramen ovale, which is largest in the early stages of preg- 

 nancy. Previously to birth, instead of two large trunks, the pulmor 

 nary artery furnishes only two small branches to the lungs; but it is 

 prolonged, under the name of the arterial canal {ductus arteriosus) 

 as far as to the aorta, into which it opens below the left subclavian 

 artery. The hypogastric branches of the primitive iliacs send only 

 small branches to the pelvic organs, which are as yet scarcely de- 

 veloped; but they rise along the sides of the bladder and urachus, 

 under the name of umbilical arteries, and proceed to the umbilical 

 ring and to the cord. Unlike the adult, the foetus also has an umbili- 

 cal vein, which, upon entering into the abdomen, proceeds back- 

 wards and upwards, and somewhat from left to right, so as to pass 

 into the longitudinal fissure of the liver, through which it passes, giv- 

 ing off" here and there a branch to the right and left lobes of the liver. 

 Having reached the under surface of the liver in the transverse fis- 

 sure, the umbilical vein divides into two trunks: one, which is called 

 the venous canal [ductus venosus), and which, like the ductus arte- 

 riosus, grows smaller and smaller as the term of gestation approaches, 

 appears to be a continuation of the primitive vein, and proceeds to 

 open into the trunk of the vena cava, below the diaphragm; the other, 

 which constitutes the right branch of the vena portae, penetrates into 

 the liver, where it at length anastomoses with the radicles of the he- 

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