VISCERA OF THE ABDOMEN. 559 



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 respira- 

 tion, the relative weight of the lung to the entire body is as 1 to 30. 



FOETAL 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 un- 

 dergoing 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 distension 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 vessels. 



The Omphalo-mesenteric are the first developed vessels of the germ : 

 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 establish- 

 ment of the placental circulation they cease to carry blood, and dwindle 

 to the size of mere threads, w r hich may be easily demonstrated in the early 

 periods of uterine life ; but are completely removed, excepting under pe- 

 culiar circumstances, at a later period. 



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

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

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

 particularly of its left lobe. 



The Appendix vermiformis c&ci is long and of large size, and is con- 

 tinued directly from the central part of the cul-de-sac of the caecum, of 

 which it appears to be a constricted continuation. This is the character 

 of the appendix caeci in the higher quadrumana. 



The large intestines are filled with a dark green viscous secretion, called 

 meconium (f^xwv, poppy), from its resemblance to the inspissated juice of 

 the poppy. 



The Pancreas is comparatively larger in the foetus than in the adult. 



The Spleen is comparatively smaller in the foetus than in the adult. 



* 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. 'JTie 

 foramen was well known to Galen. 



