446 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS. 



3. — Of the External Cells of the Villi. 



Immediately under the membrane just described is a layer 

 of cells* They are flattened spheroids, slightly quadrilateral 

 in outline, from the manner in which they are packed together. 

 Wlien a tuft is viewed in profile, under compression, its edges 

 exhibit the appearance of a double line, which leads the 

 observer to suppose that its bounding membrane is double, 

 with the cells just described situated between the two laminse. 

 In the space between the two lines, the nuclei of the cells may 

 be seen in the form of dark oval spots, and the septa formed 

 by the walls of contiguous cells are also visible. 



At variable distances the space between the two lines 

 widens out into a triangular form, the base towards the external 

 membrane, the apex towards the centre of the villus. This 

 wider space is produced by a larger group of cells, which ap- 

 pear to be passing off from a spot in the centre of the mass. 

 The groups of cells I am now describing are germinal spots. 

 They are the centres from which new cells are constantly 

 passing off, to supply the loss of those which have disappeared 

 in the performance of their important function. 



As in the case of the intestinal epithelium, I am inclined 

 to believe that a fine membrane lines the internal aspect of the 

 layer of cells. I have not been able to isolate it ; but the very 

 sharp outline in a profile view of a villus confirms me in my 

 belief of the existence of such a membrane. 



4. — Of the Internal Memlrane of the Villus. 



When a villus, under gentle compression, is viewed by 

 transmitted light, there is perceived under the structures 

 already described, and immediately bounding the blood- 



* Mr. Dalrymple, " On the Structure of the Placenta."— i/ed Chir. Trans. 

 London, vol. xxv. pages 23, 24. 



