150 PROSPECTIVE CONTRIVANCES. 



air; elaborately constructed for the alternate admission and 

 exclusion of an elastic fluid, where no such fluid exists; 

 this great organ, with the whole apparatus belonging to it, 

 lies collapsed in the foetal thorax, yet in order, and in read- 

 iness for action, the first moment that the occasion requires 

 its service. This is having a machine locked up in store 

 for a future use ; which incontestibly proves that the case 

 "was expected to occur, in which this use might be experi- 

 enced ; but expectation is the proper act of intelligence. 

 Considering the state in which an animal exists before its 

 birth, I should look for nothing less in its body than a sys- 

 tem of lungs. It is like finding a pair of bellows in the 

 bottom of the sea ; of no sort of use in the situation ia 

 which they are found ; formed for an action which was im- 

 possible to be exerted ; holding no relation or fitness to the 

 element which surrounds them, but both to another ele- 

 ment, in another place. 



As part and parcel of the same plan ought to be men- 

 tioned, in speaking of the lungs, the provisionary contri- 

 vances of the foramen ovale and ductus arteriosus. (Pi. 

 XXIX.) In the fcetus, pipes are laid for the passage of the 

 blood through the lungs ; but, until the lungs be inflated 

 by the inspiration of air, that passage is impervious, or in a 

 great degree obstructed. What then is to be done ? What 

 would an artist, what would a master do upon the occasion? 

 He would endeavour, most probably, to provide a temporary 

 passage, which might carry on the communication requir- 

 ed, until the other was open. Now this is the thing which 

 is actually done in the heart. Instead of the circuitous 

 rout through the lungs, which the blood afterwards takes, 

 before it get from one auricle of the heart to the other ; 

 a portion of the blood passes immediately from the right 

 auricle to the left, through a hole, placed in the partition 

 which separates these cavities. This hole anatomists call 

 ihe foramen ovale. There is likewise another cross cut, 

 answering the same purpose, by what is called the ductus 

 arteriosus, lying between the pulmonary artery and the 

 aota. 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 

 in the lungs, appears to be necessary to the perfect^concoc- 

 tionof that fluid, i. e. to the life and health of the animal, 

 (otherwise the shortest rout might still be the best,) how 



