842 GENERATION. 



impervious between the second and the fourth days. The hypogastric arter- 

 ies remain pervious at their lower portion and constitute the superior vesi- 

 cal arteries. A rounded cord, which is the remnant of the umbilical vein, 

 forms the round ligament of the liver. A slender cord, the remnant of the 

 ductus venosus, is lodged in a fissure of the liver, called the fissure of the 

 ductus venosus. 



CHAPTER XXVI. 



F(ETAL LIFE-DEVELOPMENT AFTER BIRTH DEATH. 



Enlargement of the uterus in pregnancy Duration of pregnancy Size, weight and position of the foetus 

 The foetus at different stages of intrafiterine life Multiple pregnancy Cause of the first contractions 

 of the uterus, in normal parturition Involution of the uterus Meconium Dextral pre-eminence De- 

 velopment after birth Ages Death Cadaveric rigidity (rigor mortis). 



As the development of the ovum advances, the uterus is enlarged and its 

 walls are thickened. The form of the organ, also, gradually changes, as well 

 as its position. Immediately after birth its weight is about a pound and a 

 half (680 grammes) while the virgin uterus weighs less than two ounces (56'7 

 grammes). The neck of the uterus, while it becomes softer and more patu- 

 lous during pregnancy, does not change its length, even in the very latest 

 periods of utero-gestation (Taylor). The changes in the walls of the uterus 

 during pregnancy are very important. The blood-vessels become much en- 

 larged, and the muscular fibres increase immensely in size, so that their con- 

 tractions are very powerful when the foetus is expelled. 



It is evident that on account of the progressive increase in the size of the 

 uterus during pregnancy, it can not remain in the cavity of the pelvis dur- 

 ing the later months. During the first three months, however, when it is 

 not too large for the pelvis, it sinks back into the hollow of the sacrum, the 

 fundus being directed somewhat backward, with the neck presenting down- 

 ward, forward and a little to the left. After this time, however, the in- 

 creased size of the organ causes it to extend into the abdominal cavity, so 

 that its fundus eventually reaches the epigastric region. Its axis then has 

 the general direction of the axis of the superior strait of the pelvis. 



The enlargement of the uterus and the necessity of carrying on a greatly 

 increased circulation in its walls during pregnancy are attended with a tem- 

 porary hypertrophy of the heart. It is mainly the left ventricle which is 

 thickened during utero-gestation, and the increase in the weight of the heart 

 at full term amounts to more than one-fifth. After delivery the weight of 

 the heart soon returns nearly to the normal standard. 



Duration of Pregnancy. The duration of pregnancy, dating from a 

 fruitful intercourse, must be considered as variable, within certain limits. 

 The method of calculation most in use by obstetricians is to date from the 

 end of the last menstrual period. Taking into account, however, the various 



