VASCULAR SYSTEM. 121 



The blood of the capillaries of the inferior extremities of 

 the abdomen and umbilical cord, instead of going from the 

 inferior cava to the right auricle, passes to the left auricle 

 through the foramen ovale, and thence through the left , 

 ventricle into the carotids and head. 



Q. Give Sabatier's second division of the foetal circu- 

 lation. 



./?. It is that the blood returning from the head, passes 

 along the right auricle, ventricle, and pulmonary artery, 

 through the ductus arteriosus into the aorta descendens, 

 thence into the capillary system of the abdomen and ex- 

 tremities, and partly to the umbilical arteries. So that 

 there are two circulations in the foetus, with different 

 origins, trunks, organs of impulse and terminations. 



Q. In this system of Sabatier, what part of the heart 

 impels the blood to the upper and lower parts of the 

 body? 



#. The left ventricle propels it to the head; the right 

 ventricle to the lower parts of the body. By the gradual 

 closure of the foramen ovale and ductus arteriosus, the 

 blood takes its channels for life; the change is not a sud- 

 den one. 



Q. Is the arterial system early developed? 



*#. Of course it is, as it conveys nutriment ; but the 

 texture is soft, yielding, apparently homogeneous. The 

 arterial strengthens as the heart increases in vigour. 



Q. What changes take place at birth? 



#. In the red blood system, two changes take place ; 

 the one is mechanical, the other is chemical. 



Q. What are these mechanical and chemical changes? 



#. The mechanical 'are the closures of the foramen 

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