CHAPTER XL 



ANATOMY OF THE FCET0S. 



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

 pounds ; and its length nineteen 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 extremi- 

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

 external genital organs are very large, and fully developed. 



OSSEOUS SYSTEM. The developement 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 fo3tus 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 fetal 

 life. 



VASCULAR SYSTEM. The circulating system presents several 

 peculiarites ; Istly, In the heart; there is a communication between 

 the two auricles by means of the foramen ovale. 2dly, In the arte- 

 rial 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 name 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 fetus. 4thly, 

 In the venous system ; there is a communication between the 

 umbilical vein and the inferior vena cava, called the ductus venosus. 



FCETAL 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 of which are dis- 

 tributed to the left lobe. 2dly, A single branch which communicates 

 with the portal vein in the transverse fissure, and supplies the right 

 lobe. 3dly, A large branch, the ductus venosus, which passes 



