UTERUS (DEVELOPMENT). 



657 



am satisfied that no such union takes place ; 

 but that, when the decidua reflexa has ful- 

 filled the offices already assigned to it, and 

 has ceased to be vascular, so that no further 

 addition of material to it can take place, it 

 becomes, after the fifth or sixth month, so 

 completely attenuated by distension from the 

 growth of the ovum within, that it is reduced 

 to a mere film, of which the only trace left 

 at, or indeed before, birth, is a narrow frill 

 still discoverable at the margin of the placenta 

 between the decidua vera and the chorion. 

 But the decidua lining the uterine walls con- 

 tinues vascular to the last ; and this alone 

 constitutes the membrane a part of which at 

 birth is found adherent to the outer surface of 

 the chorion, and which Dr. Hunter, from ob- 

 serving that it now consisted of only one 

 layer, imagined was formed of the two de- 

 ciduae united together. 



Histology of the decidua. The morpholo- 

 gical changes effected during pregnancy in the 



Fig. 454. 



Histology of the decidua. (After Schroeder van der 

 Kolk.} 



A, orifice of utricular gland of an unimpregnated 

 adult uterus surrounded by round epithelial cells ; 

 B, cells of decidua in an ovum of about three weeks ; 



a, round and oval nucleated cells ; b, fat granula- 

 tions ; c, cells, from a deeper layer, elongated and 

 beginning to form fibres ; c, the same from an ovum 

 of live weeks; a, round and oval cells, much en- 

 larged, and containing nuclei and fat granulations 

 from the surface ; b, elongated cells from a deeper 

 layer ; D, orifice of a utricular gland from the same 

 ovum, much enlarged as compared with A; E, 

 margin of a valvular opening in a deeper layer of 

 the decidua, from an ovum of two months ; at b, 

 the cells have become elongated, at a they are tilled 

 with fat granulations; F, long and broad cells from 

 a decidua of nine months; a, the cells exhibit a 

 nucleus, some having one and others two nucleoli ; 



b, three-pointed cell. 



Supp. 



decidua, and the chief purposes of these, hav- 

 ing been stated, the histological peculiarities 

 will now be briefly described. The lining 

 membrane of the uterus, from infancy on- 

 wards, is composed, as already shown, of free 

 elementary corpuscles or nuclei, contractile 

 fibre cells, amorphous tissue and epithelium, 

 together with capillary vessels, and the tor- 

 tuous canals termed uterine glands. These 

 undergo important modifications, which serve 

 to explain the great and rapid growth of the 

 decidua during pregnancy. According to 

 Schroeder van der Kolk, who has traced and 

 figured with great care the several stages of 

 development of these elemental tissues, the 

 cells of the decidua, surrounding an ovum of 

 about three weeks, situated nearest the villi, 

 have already undergone considerable enlarge- 

 ment. These occurred in the form of oval 

 nucleated cells (fig. 454. B cr), with fine 

 nuclei and fat granules, b y intermixed ; while 

 in the layer of the decidua, still deeper, oc- 

 curred longer cells, that were already begin- 

 ning to form fibres. 



In an ovum of five weeks, similar cells were 

 found, in a further stage of development. Tn 

 the superficial decidual layers, the oval cells, 

 C a, were filled with granules, and contained 

 a nucleus, and some a nucleolus. In the 

 deeper layers, as before, the cells had become 

 more elongated, C b. In and between all 

 these cells were numerous minute fat granules, 

 and among the cells lay fine nuclei. The 

 openings of the utricular glands, D, which 

 were surrounded by enlarged epithelial cells, 

 were now considerably expanded, as compared 

 with their usual condition previous to im- 

 pregnation, A. 



At two months, the increase in size of the 

 oval cells, E a, now abundantly furnished with 

 fat granules, was still more marked. These 

 were developed into long cells, b, which were 

 found composing those valve-like membra- 

 nous septa formed now everywhere on the 

 deeper decidual layer, as already described,^. 

 452. 



From this period onwards, the development 

 of the cells proceeds more and more rapidly, 

 until those in the deeper layers become trans- 

 formed into fibres, which it is impossible to 

 distinguish, under the microscope, from the 

 peculiar contractile fibre cells of the true mus- 

 cular structure. 



In the ninth month are found colossal fibre 

 cells, F a, which are rarely seen beyond the 

 margin of the placenta. These were very 

 transparent, and exhibited, some one, and 

 some two, nucleoli. A remarkable three- 

 pointed cell is sometimes also observed, F b. 

 Fibres of fibrous tissue occur everywhere, and 

 between them small cells and nuclei. The 

 utricular glands have long ceased to be dis- 

 cernible in the advanced stages of pregnancy. 



According to the observations, however, of 

 Rolin, Robin, and Kilian, from the fourth or 

 fifth month onwards, the decidua begins to 

 lose the character of energetic life, which, up 

 to that period, it had exhibited, and becomes 

 atrophied, and less firmly adherent to the 

 u u 



