402 OP THE DIFFBRECES IN THE SYSTEM 



639. The supra-renal glands, called also renes suc- 

 centuriati and capsulae atrabiliariae, lie under the dia- 

 phragm on the upper margin of the kidneys,* from 

 which, in the adult, they are rather more distant, being 

 proportionally smaller. They are full of a dark fluid 

 of a more reddish hue in the foetus than in the adult. 



NOTE. 



Blumenbach has omitted here to notice one of the most striking 

 peculiarities of the foetus, — the very great proportionate bulk of 

 its liver. The prodigious size of this organ arises from the dis- 

 tribution of four-fifths of the blood of the umbilical vein through 

 it, and probably, in a certain degree, as some think, from the 

 great quantity of meconium in its biliary ducts. After birth, no 

 blood is conveyed by the umbilical vein, and the expansion of 

 the thorax readily expresses the abundance of meconium ; hence 

 the liver must diminish.- 



This peculiarity, as well as the great size of the thyreoid, 

 thymus, and supra-renal glands, probably serves some purpose 

 hitherto, undiscovered, but an evident good effect results from it 

 in relation to the organs of the thorax. In the foetus the lungs 

 are completely devoid of air, and consequently there cannot be 

 much, if any, circulation of blood through the pulmonary artery 

 and veins, and the liver by its magnitude, protruding the dia- 

 phragm upwards, renders the capacity of the chest correspond- 

 ently small, and at the same time it contains an immense pro- 

 portion of blood. After birth, the diminished size of the liver 



• See Eustachius their discoverer, Tab. i. ii. iii. and tab. xii. fig. I. 10. 12. 

 Haller, Icohh* Anat. fasc. iii. tab. vi. 

 Malacftrne, 1. e. 



