VISCERA OF THE ABDOMEN. 559 



two ventricles form, at one period, a single cavity, which is after- 

 wards 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 Botal.)* 



The Ductus arteriosus is another peculiarity of the foetus con- 

 nected with the heart ; it is a communication between the pulmo- 

 nary 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. 

 '*'<;$" <&$J8* ; - 



B 



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-mesen- 

 teric 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 ernbryo. From 

 them, as from a centre, the general circulating system is produced. 

 After the establishment 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, except under peculiar circumstances, at a later 

 period. 



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

 developed. It is also more vertical in direction the earlier it may 

 be examined, a position that would seem due to the enormous mag- 

 nitude of the liver, and particularly of its left lobe. 



The Appendix vermifarmis cceci is long and of large size, and is 

 continued directly from the central part of the cul-de-sac of the 

 ca3cum, of which it appears to be a constricted continuation. This 

 is the character of the appendix casci in the higher quadrumana. 



The large intestines are filled with a dark green viscous secre- 

 tion called meconium (f/^xwv, poppy), from its resemblance to the in- 

 spissated 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. 



* 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. 





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