THE DEVELOPMENT OF THE UTERUS, AND THE METAMORPHOSF.S WHICH IT UNDERGOES AT DIFFERENT PERIODS OF LIFE.
a. The origin of the uterus, and its condition during falai In the human embryo, ac cording to the observations of Miller, during the transformation of the Wolffian bodies, the efferent tube of the generative apparatus un dergoes the following modifications. In the male, all that portion of the efferent tube which passes along the outer border of the corpus Wolffianum is thrown into strongly marked convolutions, and this part contributes to the formation of the epididymis, while be low this point the convolutions cease ; and here a band or ligament, the gubernaculum testis of Hunter, which had been developed at a still earlier period, passes off to the inguinal canal. In the female, the following trans formation occurs. The tube here remains free from convolutions, but a ligament, re sembling that of the male, which is afterwards converted into the ligamentum uteri teres, passes off' from the same point, to be extended to the inguinal ring. The part of the tube which lies below this point becomes the cornu uteri, and it is by the coalescence of the two cornua at their lower extremities that the body of the uterus is formed in man ; while in those animals in which no middle portion or body exists, the cornua remain ununited. As the development of the uterus proceeds, the two cornua become gradually shorter, until at length they are lost, or, as it were, absorbed into the body or fundus of the uterus, which is thus at the same time developed.
The accompanying figure, representing the condition of the fcetal uterus at about the end of the third month of gestation, serves to illustrate these particulars. The ovaries pos sess the elongated form characteristic of the early condition of these organs. Parallel with them run the Fallopian tubes, and between these are the remains of the Wolffian bodies. At the point where the round ligaments are given off, the cornua uteri begin, and by their junction, which is here not yet complete, so that a slight indentation is left, the uterus is formed.
From this period of embryonic life, the uterus keeps pace in its growth vvith the other viscera and at the time of birth it forms an organ of considerable size, lying high up in the latter is the more considerable, for the body has not yet acquired breadth ; while the cervix, forming a tube of nearly equal calibre with the body, possesses almost twice its length. This greater length of the cervix, as compared with the body of the uterus, is one of the most striking characteristics of fcetal life (fig. 44 I.), one also which continues to be observed for many years after birth.
b. The uterus from the time of birth to pu berty. —From the time of birth until the approach of puberty, the internal generative organs undergo but little change. Gradually, but slowly;increasing in size, they still retain the principal characteristics of the fcetal pe riod. The uterus consists still chiefly of cer vix, the body being that part which is last del eloped. Thus in a child of three years (fig. 442.), in whom the entire length of the uterus is 15"', the cervix measures 11"', and the body only 4'". These dimensions do not materially differ from those of the uterus in the first year of life, nor do they much exceed those of the same organ at birth.
But as puberty approaches, the relative proportions of the cervix and body of the uterus are found to have changed, and the latter now preponderates over the former. For lAhile the body now equals the cervix in length, the breadth of the former much exceeds that of the latter. The walls of the upper chamber now become thicker from the more rapid development of the uterine muscular fibre, which is their chief constituent. This not only increases the ex ternal dimensions of the organ, but, at the same time, causes the parietes to becotne in curved, and so to encroach upon the cavity contained by them, which, up to this period, preserves the form of a nearly equilateral triangle (fig. 442.), but now gradually acquires the shape already described as characteristic of the cavity of the adult uterus (fig. 431.).