NATURAL THEOLOGY. 63 



ber, and variety, be such, and may so overpower 

 apparent blemishes, as to induce us, upon the most 

 reasonable ground, to believe that these last ought 

 to be referred to some cause, though we be ignorant 

 of it, other than defect of knowledge or of benev- 

 olence in the author. 



II. There may be also parts of plants and ani- 

 mals, as there were supposed to be of the watch, of 

 which, in some instances the operation, in others 

 the use, is unknown. These form different cases: 

 for the operation may be unknown, yet the use be 

 certain. Thus it is with the lungs of animals. It 

 does not, I think, appear, that we are acquainted 

 with the action of the air upon the blood, or in 

 what manner that action is conmiunicated by the 

 lungs ; yet we find that a very short suspension of 

 their office destroys the life of the animal.*"^ In 

 this case, therefore, we may be said to know the 

 use, nay, we experience the necessity, of the organ, 

 though we be ignorant of its operation. Nearly 

 the same thing may be observed of what is called 

 the lymphatic system. We suffer grievous incon- 

 veniences from its disorder, without being inform- 

 ed of the office which it sustains in the economy 



^'' Undoubtedly the exposure of the blood to the atmosphere, in 

 the circulation through the lungs, and the throwing off of carbon, 

 are essential to life. But the pain and alarm excited when there 

 is danger of suffocation are not so much a direct consequence of 

 the interruption of the function, as an instance of the manner in 

 which the sensibility is bestowed to guard the important actions 

 of life. 



