STKUCTTJRE OF HUMAN PLACENTA. 445 



XXIX. THE STKUCTUEE OF THE HUMAN 

 PLACENTA. (PLATES V. VI.) 



I. OF THE STRUCTURE OF THE TUFTS AND VILLI OF THE 

 PLACENTA. 



1. Of the Configuration of the Tufts. 



A PLACENTAL tuft resembles a tree. It consists of a trunk, 

 of primary branches, and of secondary branches or terminal 

 villi, which are attached as solitary villi to the sides of the 

 primary branches, and to the extremities of the latter, in which 

 case they generally present a digitated arrangement. The 

 villus, when solitary, is cylindrical, .or slightly flattened, or 

 somewhat club-shaped ; when digitated, each division may be 

 much flattened, or is then generally heart-shaped. The 

 digitated villi are only solitary villi grouped together at the 

 extremity of a primary branch. 



2. Of the External Membrane of the Tufts. 



The trunk, the primary branches, and the terminal villi of 

 the tuft are covered by a very fine transparent membrane, 

 apparently devoid of any structure. This membrane may be 

 described as bounding the whole tuft, passing from the trunk 

 to the branches, and from these to the villi, the free extremities 

 of which it closely covers. Its free surface is smooth and 

 glistening its attached surface is somewhat rough.* 



* Professor Reid, " On the Anatomical Relations of the Bloodvessels of the 

 Mother to those of the Fostus in the Human Species." Ed. Med. Surg. Journal, 

 1841, page 7. 



