844 GENERATION. 



grammes). If the foetus be delivered at this time, life may continue for a 

 few moments ; the bones of the head are ossified, but the f ontanelles and 

 sutures are still wide; the prepuce has appeared; the testicles have not 

 descended. 



At the seventh month the fcetus is fourteen to fifteen inches (35-5 to 38-1 

 centimetres) long and weighs two to three pounds (907 to 1,361 grammes). 

 The hairs are longer and darker ; the pupillary membrane disappears, under- 

 going atrophy from the centre to the periphery ; the relative quantity of the 

 amniotic fluid is diminished, and the fcetus is not so free in the cavity of the 

 uterus ; the fcetus is now viable. 



At the eighth month, the fcetus is fifteen to sixteen inches (38'1 to 40-9 

 centimetres long and weighs three to four pounds (1,361 to 1,814 grammes). 

 The eyelids are opened and the cornea is transparent ; the pupillary membrane 

 has disappeared ; the left testicle has descended ; the umbilicus is at about the 

 middle of the body, the relative size of the lower extremities having increased. 



At the ninth month the foetus is about seventeen inches (43'2 centimetres) 

 long and weighs five to six pounds (2'27 to 2'72 kilos). Both testicles usu- 

 ally have descended, but the tunica vaginalis still communicates with the 

 peritoneal cavity. 



At birth the infant weighs a little more than seven pounds (3-17 kilos), 

 the usual range being between four and ten pounds (1*81 and 4'53 kilos), 

 although these limits are sometimes exceeded. 



The position of the foetus, in the great majority of cases, excluding ab- 

 normal presentations, is with the head downward. In the early months of 

 pregnancy the fcetus floats quite freely in the amniotic fluid ; and it is prob- 

 able that the natural gravitation of the head and of the upper part of the 

 foetus is the determining cause of the ordinary position in utero. 



The shape of the uterus at full term is ovoid, the lower portion being the 

 narrower. The foetus has the head slightly flexed upon the sternum, the 

 arms flexed upon the chest and crossed, the spinal column curved forward, the 

 thighs flexed upon the abdomen, the legs slightly flexed and usually crossed 

 in front, and the feet flexed upon the legs, with their inner margin drawn 

 toward the tibia. This is the position in which the fcetus is best adapted to 

 the size of the uterine cavity, and in which the expulsive force of the uterus 

 can be most favorably exerted, both as regards the foetus and the generative 

 passages of the mother. 



Multiple Pregnancy. It is not very rare to observe two children at a 

 birth, and cases are on record where there have been four and even five, 

 though in these latter instances the children generally survive but a short 

 time, or as is more common, abortion takes place during the first months. 

 Examples of three at a birth have been often observed. 



In cases of twins it is an interesting question to determine whether the 

 development always takes place from two ova or whether a single ovum may 

 be developed into two beings. In the majority of cases, twins are of the 

 same sex, though sometimes they are male and female. In some cases there 

 are two full sets of membranes, each foetus having its distinct decidua, pla- 



