THE GLANDS OF THE UTERUS. 589 



structure, these little outgrowths subsequently become vascular 

 by the development in them of loops of capillaries (Fig. 225) ; 

 and the latter at length form the minute extremities of the 

 bloodvessels which are, so to speak, conducted from the foetus 

 to the chorion by the allantois. The function of the villi of 

 the chorion is evidently the absorption of nutrient matter for 

 the fcetus ; and this is probably supplied to them at first from 

 the fluid matter secreted by the follicular glands of the uterus, 

 in which they are soaked. Soon, however, the foetal vessels 

 of the villi come into more intimate relation with the vessels 

 of the uterus. The part at which this relation between the 

 vessels of the foetus and those of the parent ensues, is not, how- 

 ever, over the whole surface of the chorion : for, although all 

 the villi become vascular, yet they become indistinct or dis- 

 appear except at one part where they are greatly developed, 

 and by their branching give rise, with the vessels of the uterus, 

 to the formation of the placenta. 



To understand the manner in which the/te&z/ and maternal 

 bloodvessels come into relation with each other in the pla- 

 centa, it is necessary briefly to notice the changes which the 

 uterus undergoes after impregnation. These changes consist 

 especially of alterations in structure of the superficial part of 

 the mucous membrane which lines the interior of the uterus, 

 and which forms, after a kind of development to be immedi- 

 ately described, the membrana deddua, so called on account 

 of its being discharged from the uterus at the period of partu- 

 rition. 



Changes of the Mucous Membrane of the Uterus, and Formation 

 of the Placenta. 



The mucous membrane of the human uterus is abundantly 

 beset with tubular follicles, arranged perpendicularly to the 

 surface. These follicles are very small in the unimpregnated 

 uterus ; but when examined shortly after impregnation, they 

 are found elongated, enlarged, and much waved and contorted 

 towards their deep and closed extremity, which is implanted 

 at some depth in the tissue of the uterus, and commonly dilates 

 into two or three closed sacculi (Fig. 226). 



According to Dr. Sharpey, the glands of the mucous mem- 

 brane of the bitch's uterus (and according to H. Miiller, that 

 of the human female also) are of two kinds, simple and com- 

 pound. The former, which are the more numerous, are merely 

 very short unbranched tubes closed atone end (Fig. 227, 1, 1,), 

 the latter (2, 2) have a long duct dividing into convoluted 

 branches ; both open on the inner surface of the membrane by 



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