44 OBSTETRICS. 



corrected by the time at which quickening occurs, the latter occur- 

 rence usually taking place at four months and a half. 



Extra-uterine pregnancy. It occasionally happens that the ovum, 

 instead of passing down the Fallopian tube to the uterus, is arrested 

 in its progress, and an effort is made at the point of obstruction to 

 afford space and nutrition for the foetus. When the ovum is de- 

 tained and developed in the ovary, it is called ovarian pregnancy. 

 O? this variety Dr. Granville relates a case in the Lond. Phil. 

 Transactions, part 1, 1820. When the Fallopian tube is the seat 

 of the arrest, it is called tubal pre gna7icy ; of this variety cases are 

 reported by Dr. R. Lee in the Lond. Med. Gaz., vol. xxvi, p. 436. 

 Also by Dr. Meigs, vide his work, p. 106. It sometimes happens 

 that the ovum enters the parietes of the uterus, constituting a third 

 and rare description called interstitial pregnancy. A fourth variety 

 is called ventral or abdominal preg7iancij^ where the ovum falls 

 into the abdominal cavity, attaches itself, and is developed there. 

 It is worthy of remark, that in all these varieties, the uterus is lined 

 with a deciduous membrane, as it is in iyitra-uterine pregnancy. 



The causes are not well known, and the treatment can be merely 

 palliative. Portions of the foetus are often discharged from fistulous 

 openings in the abdomen, vagina, or rectum. 



Fcetal circulation. — The peculiarities of the foetal circulation, in 

 which it differs from that function in the adult are, 1st. The ductus 

 venosus, a supplementary vein, situated at the thick edge of the liver, 

 and leading from the umbilical vein to the vena cava ascendens. 

 2d. The aperture between the right and left auricle, effecting a com- 

 munication between them, called the forar/ien ovale. 3d. The ductus 

 arteriosus, a branch given off from the pulmonary artery soon after 

 its origin, which conducts the venous blood that has arrived at the 

 heart from the head into the aorta just below its arch. 



The following is the route of the circulation in the foetus, starting 

 from the placenta. The blood, after being aerated in this organ, is 

 collected by the umbilical veiii, which carries it to the umbilicus of 

 the child. After entering the cavity of the abdomen, the current 

 divides, part of it being sent through the vena? portarum to the 

 liver ; the remainder reaches the vena cava ascendens through the 

 ductus venosus, where it is mixed with the blood from the inferior 

 extremities. The blood that was sent to the liver is collected by 

 the hepatic veins and also emptied into the vena cava ascendens, 

 which finally discharges its contents into the right auricle of the 

 heart. From the right auricle, it is directed by the Eustachian 

 valve through the foramen ovale, into the left auricle, thence it 

 passes into the left ventricle, by which it is distributed through the 

 aorta to the system, a large proportion of it going to the head and 

 upper extremities. The latter blood, (that from the head, &c.,) is 



