846 GENERATION. 



gradually dilate the cervix ; the membranes usually rupture when the os is 

 pretty fully dilated, and the amniotic fluid is discharged ; the head then 

 presses upon the outlet ; and the uterine contractions becoming more and 

 more vigorous and efficient, the child is brought into the world, this being 

 followed by the expulsion of the membranes and placenta. There then fol- 

 lows a tonic contraction of the muscular walls of the uterus, which becomes 

 a hard, globular mass, easily felt through the flaccid, abdominal walls. The 

 very contractions of the muscular fibres of the uterus which expel the foetus 

 close the vessels ruptured by the separation of the placenta and arrest the 

 haemorrhage from the mother. The changes which then take place in the 

 respiration and the circulation of the infant have been considered in connec- 

 tion with the development of the circulatory system. 



Involution of the Uterus. At four to six days, and seldom later than 

 eight days after parturition, the uterus has sensibly advanced in the process 

 of involution ; and it is then gradually reduced to the size and structure 

 which it presents during the non-pregnant condition, though it never be- 

 comes quite as small as in the virgin state. The new mucous membrane, 

 which has been developing during the latest periods of pregnancy, becomes 

 perfect at about the end of the second month after delivery. It has then 

 united, at the os internum, with the mucous membrane of the neck, which 

 has not participated in the formation of the decidua. The muscular fibres, 

 after parturition, present granules and globules of fat in their substance, and 

 are gradually reduced in size as the uterus becomes smaller. Their involu- 

 tion is complete at about the end of the second month. During the first 

 month, and particularly within the first two weeks after delivery, there is a 

 sero-sanguinolent discharge from the uterus, which is due to disintegration 

 of the blood and of the remains of the membranes in its cavity, this debris 

 being mixed with a certain quantity of sero-mucous secretion. This dis- 

 charge constitutes the lochia. It is at first red but becomes paler as it is 

 reduced in quantity and disappears. 



Meconium. At about the fifth month there is a certain quantity of 

 secretion in the intestiaal canal, which becomes more abundant, particularly 

 in the large intestine, as development advances. This is rather light-colored 

 or grayish in the upper portion of the small intestine, becoming yellowish in 

 the lower portion, and it is of a dark-greenish color in the colon. The dark, 

 pasty, adhesive matter, which is discharged from the rectum soon after birth, 

 is called the meconium. 



The meconium appears to consist of a thick, mucous secretion, with 

 abundant, grayish granules, a few fatty granules, intestinal epithelium, and 

 frequently crystals of cholesterine. The color seems to be due to granula- 

 tions of the coloring matter of the bile, but the biliary salts can not be de- 

 tected in the meconium, by Pettenkofer's test. The constituent of the me- 

 conium which possesses the greatest physiological importance, is cholesterine. 

 Although but few crystals of cholesterine are found upon microscopical 

 examination, the simplest processes for its extraction will reveal the presence 

 of this substance in large quantity. In a specimen of meconium in which a 



