624 FffiTAL HEART. VISCERA OP THE ABDOMEN. 



respired will float upon that fluid. The specific gravity is, however, 

 no test of the real weight of the lung, the respired lung being actually 

 heavier than the foetal. Thus the weight of the foetal lung, at about 

 the middle period of uterine life, is to the weight of the body as 1 to 

 60.* But, after respiration, the relative weight of the lung to the 

 entire body is as 1 to 30. 



POSTAL HEART. 



The Heart of the foetus is large in proportion to the size of the body; 

 it is also developed very early, representing at first a simple vessel, 

 and undergoing various degrees of complication until it arrives at the 

 compound character which it presents after birth. The two ventricles 

 form, at one period, a single cavity, which is afterwards divided into 

 two by the septum ventriculorum. The two auricles communicate up 

 to the moment of birth, the septum being incomplete, and leaving a 

 large opening between them, the foramen ovale (foramen of Botalf). 



The Ductus arteriosus is another peculiarity of the foetus connected 

 with the heart ; it is a communication between the pulmonary artery 

 and the aorta. It degenerates into a fibrous cord after birth, from the 

 double cause of a diversion in the current of the blood towards the 

 lungs, and from the pressure of the left bronchus, caused by its dis- 

 tension with air. 



VISCERA OF THE ABDOMEN. 



At an early period of uterine life, and sometimes at the period of 

 birth, as I have twice observed in the imperfectly developed foetus, 

 two minute fibrous threads may be seen passing from the umbilicus 

 to the mesentery. These are the remains of the omphalo-mesenteric 



The OmpJialo-mesenteric are the first developed vessels of the gerin : 

 they ramify upon the vesicula umbilicalis, or yolk-bag, and supply the 

 newly formed alimentary canal of the embryo. From them, as from a 

 centre, the general circulating system is produced. After the estab- 

 lishment of the placental circulation they cease to carry blood, and 

 dwindle to the size of mere threads, which may be easily demonstrated 

 in the early periods of uterine life ; but are completely removed, ex- 

 cepting under peculiar circumstances, at a later period. 



The Stomach is of small size, and the great extremity but little de- 

 veloped. It is also more vertical in direction the earlier it is examined, 

 a position that would seem due to the enormous magnitude of the liver, 

 and particularly of its left lobe. 



The Appendix vermiformis coed is long and of large size, and is con- 



* Cruveilhier, Anatomie Descriptive, vol. ii. p. 621. 



f Leonard Botal, of Piedmont, was the first of the moderns who gave an 

 account of this opening, in a work published in 1565. His description is very 

 imperfect. The foramen was well known to Galen. 





