STKUCTUKE OF HUMAN PLACKiNTA. 449 



tlie wavy open loop, occur in the flattened and heart-shaped 

 villi. The contorted and otlier varieties of loops exist in the 

 club-shaped and tuberose villi* 



Lastly, It must be stated as a fact first recorded and 

 represented by Professor Weber, confirmed by the observations 

 of Mr. John Daliyniple, and to the accuracy of -which I can 

 testify, that the same peculiar vessel, or umbilical capillary, 

 may enter and retire from two or more villi 1)efore it becomes 

 continuous with a vein. 



G. — Oj tlic internal Cells of th- Villus. 



Within the internal membrane, and on the extenial 

 surface of the umbilical capillaries, are cells which I have 

 named the internal cells of the tuft. \Mien the vessels are 

 engorged, these cells are seen with difliculty, ^^^len the 

 vessels are moderately distended, and the internal membrane 

 separated from the external cells by moderate pressure, the 

 cells now under consideration come into view. They are best 

 seen in the spaces left between the internal membrane and the 

 retiring angles formed by the coils and loops of the vessels, 

 and in the vacant spaces formed by these loops. Tliese cells are 

 egg-shaped, highly transparent, and are defined by the instru- 

 ment with difficulty ; but their nuclei are easily perceived. 

 They appear to be filled with a transparent highly refractive 

 matter. This system of cells fills the whole space which 



* Mr. Dalr)Tiiplc, in liis paper on the Placenta, in the Med. Chir. Tram., 

 has described with great accuracy the manner iu wliich tlie foetal vessels ramify 

 and coil in the tufts of the placenta. 1 aiu indihted to Mr. Dulrjnnple for 

 sjwcimens of his injections of the placenta ; and to Dr. Julm Keid, for a jtortion 

 of a placenta injected hy Professor "NVil>er of Leipsic, and have satisfied myself 

 of the accuracy of the descriptions given by these anatomists. My own obser- 

 vations have been made on the unprej>ared placenta. The drawings of the 

 fuDtal vessels in Dr. Reid's jiiiper are plans, as the only iKjint he was an.xious 

 to establish wa.s, that tlie villi tenninated in blunt extremities imconnected by 

 cellular or otlier textures, the fcctal vessels returning uixtu themselves. — Reid, 

 in Edinburijh Medical a)id Sttr^ical Journal. 



2 c. 



