616 



CHAPTER XL 



ANATOMY OF THE FCETUS. 



THE medium weight of a child of the full period, at birth, is seven 

 pounds, and its length seventeen inches ; the extremes of weight are 

 four pounds and three quarters, and ten pounds, and the extremes of 

 measurement fifteen and twenty inches. The head is of large size, 

 and lengthened from before backwards ; the face small. The upper 

 extremities are greatly developed, and the thorax expanded and full. 

 The upper part of the abdomen is large, from the great size of the 

 liver ; the lower part is small and conical. And the lower extremities 

 are very small in proportion to the rest of the body. The external 

 genital organs are very large, and fully developed, and the attachment 

 of the umbilicus is one inch farther from the vertex of the head than 

 from the soles of the feet ; and one inch farther from the ensiform car- 

 tilage than the symphysis pubis. 



OSSEOUS SYSTEM. The development of the osseous system has 

 been treated of in the first Chapter. The ligamentous system pre- 

 sents no peculiarity deserving of remark. 



MUSCULAR SYSTEM. The muscles of the foetus at birth are large 

 and fully formed. They are of a lighter colour than those of the adult, 

 and of a softer texture. The transverse striae upon the fibres of 

 animal life are not distinguishable until the sixth month of fatal 

 life. 



VASCULAR SYSTEM. The circulating system presents several pe- 

 . culiarities ; 1 stly, In the heart ; there is a communication between the 

 two auricles by means of the forarn&n^ovale. ~291y, In the arterial 

 system ; there is a communication between the pulmonary artery and 

 descending aorta, by means of a large trunk, the ductus arteriosus. 

 3dly, Also in the arterial system ; the internal iliac arteries, under 

 the number of hypogastric and umbilical, are continued from the fetus 

 to the placenta, to which they return the blood which has circulated 

 in the system of the foetus. 4thly, In the venous system ; there is a 

 communication between the umbilical vein and the inferior vena cava, 

 called the ductus venosus. 



FffiTAL CIRCULATION. 



The pure blood is brought from the placenta by the umbilical vein. 

 The umbilical vein passes through the umbilicus and enters the liver, 

 where it divides into several branches, which may be arranged under 

 three heads: Istly, Two or three, which are distributed to the left 



