Bauhaus-Universität Weimar

844 
STRUCTURE OF THE DECIDUA. 
of the uterus are prolonged into this product. The thickness of the 
membrane sometimes equals from one to three lines. Its outer surface 
is intimately connected with the uterus, and when artificially detached, 
or separated spontaneously, is rough, while its inner surface is smooth. 
The relation which the decidua bears to the openings of the uterus is 
not always the same: it is sometimes closed at the lower orifices of the 
Fallopian tubes, and at the upper entrance of tfie cervix uteri; some¬ 
times it is open at all these points or at one or other of them. R. Wagner 
(Meckel’s Archiv. 1S30, and Physiologie, p. 114-117.) is quite correct 
in statins- that all these varieties may occur. The cervix uteri is occu- 
pied by a mere gelatinous mucus. 
When the ovum enters the uterus, it becomes imbedded in the structure of the 
decidua which is yet quite soft. The earliest ova which have been observed in 
connection with the decidua, were not contained free in its cavity, but appeared 
to be implanted in it or pressed into it from without; the decidua, at the point of 
entrance of the ovum, being protruded inwards, and the ovum contained in a hollow 
of its external surface. (See Bock, de Membrana deciduà. Bonnæ, 1831.) During the 
further growth of the ovum, the decidua becomes more and more inverted at this point, 
the inverted part being received into the cavity of the rest of the membrane. This 
inverted portion is called the decidua reflexa, while the other part of the membrane is 
called the decidua vera. The decidua vera and the decidua reflexa have the same 
structure, which differs totally from that of the mucous membrane of the uterus. They 
are, in fact, new products. It must not be imagined that the process by which the 
decidua reflexa is formed, is a mechanical one, that the ovum, as it enters the uterus, 
pushes the membrane before it; for, like all processes of the same kind, which occur 
in the animal organism, this one is effected by the vital vegetative action exerted in a 
determinate direction. The cavity of the decidua between the decidua vera and the 
decidua reflexa, contains an albuminous fluid, the “ hydroperione” of Breschet. At the 
part where the uterine expansion of the decidua is interrupted by the reflexion inwards 
of the decidua reflexa, and wfliere the ovum entered, the place of the former membrane 
is supplied by another mass similar to it, and connected at its margins with it, the 
“decidua serotina.” When young ova are examined in the uterus both the decidua 
vera and the decidua reflexa are generally found; but in aborted ova this is seldom the 
case, a part of the decidua being most frequently retained in the uterus. As the ovum 
increases in size, the decidua vera and the decidua reflexa gradually come into contact, 
and in the third month of pregnancy the cavity between them has quite disappeared. 
Henceforth it is very difficult, or even quite impossible to distinguish the two layers. 
During the further growth of the ovum the decidua becomes still thinner, but is not 
entirely lost. At birth a part of it remains behind in the uterus, while a part comes 
away, forming a thin membranous covering of the ovum.* 
The first connection which subsists between the ovum and the de¬ 
cidua, consists in the ramified villi of the chorion becoming imbedded 
in the hollow canals which traverse the decidua. The villi extend 
through these canals in the manner of roots, and thus draw nourish¬ 
ment from a maternal structure without having any organic connection 
therewith. 
According to the recent researches of E. H. Weber communicated to 
me in manuscript, the decidua is composed in greater part of the tubular 
follicles, which he very closely arranged at the inner surface of the 
uterus, and of numerous blood-vessels ramifying upon, and between 
them. In animals, the long tubular follicles, here and there bifurcated, 
lie in the substance of the uterus itself, and open upon its inner surface 
paper, in Froriep’s Notiz. 1838. No. 112, p. 22. See also R. Wagner, Physiologie, 
p. 114, and Icon Physiol. Tab. xi. fig. 5 and 6. . . 
* Respecting the decidua of the mature ovum, consult Bischoff, Beiträge zur Lehre von 
den Eihüllen des menschlichen Fötus. Bonn, 1834.
        

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