174 NATURAL THEOLOGY. 



the aorta. But both, expedients are so strictly temporary, 

 that after birth the one passage is closed, and the tube which 

 forms the other shrivelled up into a ligament. If this be not 

 contrivance, what is ? 



But, forasmuch as the action of the air upon the blood m 

 the lungs appears to be necessary to the perfect concoction 

 of that fluid, that is, to the life and health of the animal — 

 otherwise the shortest route might still be the best — how 

 comes it to pass that the fcstus lives and grows and thrives 

 without it ? The answer is, that the blood of the foetus is 

 the mother's ; that it has undergone that action in her habit ; 

 that one pair of lungs serves for both. When the animals 

 are separated, a new necessity arises ; and to meet this ne- 

 cessity as soon as it occurs, an organization is prepared. It 

 is ready for its purpose ; it only waits for the xtmosphere ; i\ 

 •■^giup to play the moment the air is admitted to it. 



