Human embryology / by Charles Sedgwick Minot.

  • Charles Sedgwick Minot
Date:
1892
Catalogue details

Licence: Public Domain Mark

Credit: Human embryology / by Charles Sedgwick Minot. Source: Wellcome Collection.

    60/854 page 28
    CHAPTEK II. GENERAL OUTLINE OF HUMAN DEVELOPMENT. This chapter is designed especially for the convenience of stu- dents of medicine and biology. Advanced students will find in it little of value to them, since all the subjects it considers are more fully treated in other portions of the volume. I. Retrogressive History of the Fcetus and its Envelopes. Uterus Eight Months Pregnant.—If we examine a pregnant uterus at any time during the sixth to ninth month of gestation, we find essentially the same relations of the parts—the most marked difference being in the size of the uterus, which increases with the duration of gestation, to correspond to the growth of the foetus. A description of a uterus of the eighth month after conception will suffice, therefore, for our present purpose. Such a uterus is a large, rounded bag, with muscular walls, and measures seven or eight inches in diameter. It renders the abdomen very protuberant. Examined externally it is remarkable especially for the numerous large sinus-like blood-vessels; its surface is smooth; the texture of the walls is firm to the touch, but the walls yield to pressure, so that the position of the child can be felt. As the placenta is generally upon the dorsal side, it is usual to open the uterus by a crucial incision upon the ventral side. The walls are about one-half of an inch thick, sometimes more, sometimes less, and as soon as they are cut open we enter at once into the cavity of the uterus containing the foetus and nearly a pint of serous liquid— the liquid is the amniotic fluid. The foetus normally lies on one side, has the head bent forward, the arms crossed over the chest, the thighs drawn against the abdomen, and the legs crossed; it resembles closely the child at birth, but is smaller; its head is relatively to the size of the body larger; the abdomen is more protuberant, and the limbs proportionately smaller. The inner surface of the uterus is smooth and glistening; if it is touched with the finger it is found to be covered by a thin but rather tough membrane, called the amnion, which is only loosely attached. Examination of the uterine wall, where it has been cut through, shows that its thickness is formed principally by the muscular layer, which is made up by numerous laminae of fibres, between which are the large and crowded blood sinuses, similar to those distinguishable on the external surface of the uterus. About one-fifth or less of the wall inside the mus- cularis has a different texture and can be partly peeled oflp as two distinct membranes, the innermost • of which is the amnion already mentioned, and the outer is the chorion united with the decidua. The amnion and chorion are appendages of the embryo; the de-
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