REPRODUCTION. 



861 



Pregnancy. With the impregnation of the ovum pregnancy 

 begins. Menstruation is arrested, and nausea or morning sickness 

 ensues. At the end of the second month the nipple swells, becomes 

 more erect, and projects forward. Then the areola of the nipple 

 enlarges, becomes puffy, and deepens in color. Toward the fifth 

 month the mammary glands increase in size. As to the genitals, 

 the mucous membrane of the vagina becomes of a violet hue, the 

 vaginal part of the cervix grows softer, a peculiar velvety softness 

 at the end of the third month. At the end of the third month the 

 uterus is the size of a foetal head, of certain doughy, elastic feel. 

 About the sixteenth week active spontaneous foetal movements are 



felt, popularly known as "quickening." 

 From the eighteenth week up to the end of 

 pregnancy the foetal heart-sounds are 

 heard, which vary from 120 to 160 per 

 minute. During the last three months 

 the uterus becomes more distended, its 

 walls are more muscular and vascular. 

 After a period of 280 days of gestation 

 labor begins, and the contents of the 

 uterus are expelled. At birth the ligature 

 of the umbilical cord cuts off the placental 

 circulation. The placenta, being now a 

 foreign body in the uterus, is expelled. 

 The ruptured and opened vessels of the 

 uterus are closed by the contraction of its 

 walls, and haemorrhage is avoided. The 



mother must eliminate during pregnancy not only the waste of her 

 own organism, but also that of the foetus. Hence the kidneys, being 

 overworked, are occasionally the cause of ursemic convulsions. 



. ACTION OF AGENTS UPON UTERUS. Fardon has shown that 

 adrenalin increases the contractions of a pregnant uterus. Shaefer 

 has shown that the pituitary extract augments the contractions of 

 the uterus. 



Ott and Scott have shown that the ovary, sperm ine, iodothyrin, 

 pancreas, mammary gland and dried brain produced strong uterine 

 contractions. This action of the ovary has been confirmed by Bell and 

 Hick. Calcium salts and the secretion from the internal surface of 

 the uterus stimulate contraction of the uterus, according to Bell 

 and Hick. 



ENLARGEMENT OF MAMMARY GLANDS IN PREGNANCY. Starling 

 found that the injections of a part of the dried embryo of rabbits 



Fig. 392. Virginal Uterus. 

 (GRANDIN and JAEMAN.) 



