THE UTERUS. 1133 
coat is firmer and more fibrous than in the body, and its surface is not smooth, but 
presents a number of peculiarly disposed ridges, which have been already described. 
Like the mucous membrane of the body of the uterus, that of the cervix is covered by a 
ciliated epithelium which passes into squamous epithelium just inside the external os uteri. 
The cervix uteri possesses, in addition to unbranched tubular glands, resembling those 
present in the body, numerous somewhat branched glands (glandule cervicales uteri). 
Both kinds of glands are lined by ciliated epithelium. In many cases little clear re- 
tention cysts, ovules of Naboth, are to be seen in the cervical mucous membrane, which 
arise as a result of obstruction at the mouths of the glands. 
Difference in the Uterus at Different Ages.—At birth the cervix uteri is 
relatively larger than in the adult organ, and its cavity is not distinctly marked 
off from the interior of the body by an internal os uteri. At this time also the 
arbor vitee extends throughout the whole length of the uterus. The organ grows 
slowly until just before puberty, when its growth is rapid for a time. As the 
body increases in size the mucous membrane becomes smooth and the arbor vite 
becomes restricted to the cervix. In women who have borne children the cavity 
remains permanently somewhat wider and larger than in cases where the uterus 
has never been pregnant. 
In old age the uterine wall becomes harder and has a paler colour than it 
possesses In the young subject. 
Variations.—In rare cases the uterus may be divided by a septum into two distinct cavities, 
or its lateral angles may be produced into straight or curved processes, called “horns” or cornua. 
The latter abnormality recalls the appearance of the bicornuate uteri of some animals. Both the 
above conditions arise from an arrest in the fusion of the two separate tubes—the MiiUerian 
ducts—which normally unite to form the uterus. 
Periodic Changes in the Uterine Wall.—At each menstrual period a remark- 
able series of changes occurs which results in the periodic shedding of the super- 
ficial parts of the uterine mucous membrane. For a few days before menstruation 
begins, the mucous membrane gradually thickens and becomes more vascular, while 
at the same time its surface becomes uneven. Soon the superficial parts of the 
mucous membrane disintegrate and hemorrhage takes place from the small super- 
ficial blood-vessels. In this way a hemorrhagic discharge is caused, and the 
superficial parts of the uterime mucous membrane are shed at each period. When 
menstruation is over the mucous membrane is rapidly regenerated. 
Pregnant Uterus.—The pregnant uterus increases rapidly in size and weight, 
so that from being three inches in length and one ounce in weight, it becomes by 
the eighth month about seven or eight inches in length and sometimes as much 
as two pounds in weight. In shape the uterus is now oval or rounded, with a thick 
wall composed chiefly of muscle fibres arranged in distinct layers. The rounded 
fundus is very prominent. The round ligaments are stronger and better marked, 
and the layers of the broad ligament become separated in their inner parts by the 
growth of the uterus between them. The blood-vessels, especially the arteries, are 
very large and tortuous. The changes which occur in the mucous membrane of 
the pregnant uterus are intimately connected with the manner in which the 
developing fcetus receives its nutrition, and have been noticed on p. 51. 
Vessels and Nerves of the Uterus—The uterus receives its arterial supply from the 
uterine arteries, which are branches of the internal iliac arteries, and also from the ovarian arteries, 
branches of the aorta. The vessels derived from these two sources communicate freely with one 
another. Each uterine artery, reavhing the side of the lower part of the uterus, div ides into a 
large branch which passes upwards to Supply the body and fundus, and a much smaller branch 
which passes downwards to supply the cervix. The vessels distributed to the body and fundus 
have an excéedingly tortuous course. The branches of the uterine artery, having entered the 
muscular coat, break up within its deeper layers into smaller twigs which supply “the muscular 
tissue and the mucous coat. The small uterine branch from the ovarian artery reaches the 
uterus in the region of the lateral angle. During pregnancy the arteries become enormously 
enlarged. 
The thin walled veins form a plexus which pours its blood into the tributaries of the internal 
iliac vein. 
The nerves of the uterus are derived chiefly from a plexus placed in the neighbourhood of 
the cervix uteri, to which the term cervical ganglion or plexus utero- vaginalis is applied. 
Superiorly this plexus i is continuous with the hypogastric plexus, but it also receives fibres from 
