1138 THE REPRODUCTIVE ORGANS 



entrance being obliterated very soon thereafter by the coalescence of 

 the edges of the opening. 



Pregnancy. — With the descent of the ovum, the woman begins 

 to exhibit very characteristic local and general signs of pregnancy. 

 The virgin uterus is small, pear-shaped, almost solid, and only 6.5 cm. 

 in length. At the end of pregnancy, on the other hand, it has been 

 converted into a large thin-walled sac, measuring 32 cm. in length, 

 24 cm. in breadth, and 22 cm. in depth. Its volume, which now 

 amounts to 5000-7000 c.c, has been increased 519 times, and its weight 

 from 32 grams to 1000 grams. This hypertrophy really begins with 

 the moment of conception, and while all of its elements are involved 

 in this process, it affects more particularly its smooth muscle-cells. 

 The latter increase not only in their length and thickness, but also in 

 their number. A similar proliferation takes place in the elastic tissue 

 and mucous membrane, which attains a thickness of almost 0.5 cm. 

 by the time the ovum has entered the uterine cavity and of 0.75 cm. 

 at the end of the second month after conception. At the end of preg- 

 nancy, the uterine wall shows an average thickness of only 3-5 mm. 

 These changes account for the fact that the cervix uteri loses its firm 

 and almost cartilaginous consistency within a few weeks after con- 

 ception. A similar change is noted very shortly before the onset of 

 each menstrual flow. 



The vascularity of the ovaries is increased, but ovulation ceases 

 as a rule during pregnancy. For this reason, it is not difficult to 

 detect the corpus luteum formed in the place of the impregnated 

 ovum. The vaginal wall also becomes more vascular and assumes a 

 peculiar violet color. Tts tissue is strengthened by new elements and 

 so is that of the vulva. Possibly the most striking change is exhibited 

 by the mammae which alter their consistency and size as well as color. 

 Already during the second month of pregnancy, these organs become 

 tense and nodular and are permeated by numerous large veins which 

 are sharply outlined against the lighter glandular tissue. The nipples 

 increase in size, become more erectile and assume a much deeper 

 color. The areola surrounding each becomes much broader, assumes 

 a darker color, and acquires numerous globular elevations which find 

 their origin in an enlargement of the sebaceous glands. Owing to the 

 increased distention of the integument, striae may be formed 

 which closely resemble those noted in the wall of the abdomen of 

 multipara. This enlargement of the mammae results in consequence 

 of the discharge of a specific hormone by the sexual organs. Quite 

 aside from the experiments of Claypon and Starling upon virgin rabbits, 

 which have been cited above but have more recently been criticized 

 by Frank and Unger,^ this conclusion is fully justified by the observa- 

 tions of Schants,^ upon the Blazek sisters, a pygopagous twin. One 



1 Archiv of Int. Med., vii , 1911, 812. 



2 Gynec. Rundschau, iv, 1910, 437. 



