FORMATION OF THE DECIDUA. 



615 



Fig. 2] 7. 



UTERINE Mucors MEMBRANE, as 

 *een in vertical section, a. Free surface. 

 b. Attached surface. 



Fig. 218. 



from that of other parts. It consists, throughout, of minute 

 tubular follicles, ranged side by side, and running perpendicularly 

 to the free surface of the mucous membrane. (Fig. 217.) Near 

 this free surface, they are nearly 

 straight; but toward the deeper sur- 

 face of the mucous membrane, where 

 they terminate in blind extremities, 

 they become more or less wavy or 

 spiral in their course. The tubules 

 are about T J 5 of an inch in diameter, 

 and are lined throughout with co- 

 lumnar epithelium. (Fig. 218.) They 

 occupy the entire thickness of the ute- 

 rine mucous membrane, their closed 

 extremities resting upon the subjacent 



muscular tissue, while their mouths open into the cavity of the ute- 

 rus. A few fine bloodvessels penetrate the mucous membrane from 

 below, and, running upward 

 between the tubules, encircle 

 their superficial extremities 

 with a capillary network. 

 There is no areolar tissue in 

 the uterine mucous mem- 

 brane, but only a small quan- 

 tity of spindle-shaped fibro- 

 plastic fibres, scattered be- 

 tween the tubules. 



As the fecundated egg is 

 about to descend into the 

 cavity of the uterus, the mu- 

 cous membrane, above de- 

 scribed, takes on an increas- 

 ed activity of growth and 

 an unusual development. It 

 becomes tumefied and vascular ; and, as it increases in thickness, it 

 projects, in rounded eminences or convolutions, into the uterine 

 cavity. (Fig. 219.) In this process, the tubules of the uterus in- 

 crease in length, and also become wider ; so that their open mouths 

 may be readily seen by the naked eye upon the uterine surface, as 

 numerous minute perforations. The bloodvessels of the mucous 

 membrane also enlarge and multiply, and inosculate freely with 



UTRRIXE Tc BULKS, from mucous membrane of 

 uuimpregnated human uterus. 



