NATURAL THEOLOGY. 145 



have a specific contrivance for dividing the pneu- 

 matic part from the mechanical, and for prevent- 

 ing one set of actions interfering with the other. 

 Where various functions are united, the difficulty 

 is to guard against the inconveniences of a too 

 great complexity. In no apparatus put together 

 by art and for the purposes of art, do I know such 

 multifarious uses so aptly combined, as in the 

 natural organization of the human mouth; or 

 where the structure, compared with the uses, is so 

 simple. The mouth, with all these intentions to 

 serve, is a single cavity ; is one machine ; with 

 Its parts neither crowded nor confused, and each 

 unembarrassed by the rest : each at least at liber- 

 ty in a degree sufficient for the end to be attained. 

 If we cannot eat and sing at the same moment, 

 we can eat one moment and sing the next : the 

 respiration proceeding freely all the wiiile. 



There is one case, however, of this double of- 

 fice, and that of the earliest necessity, which the 

 mouth alone could not perform; and that is, car- 

 rying on together the two actions of sucking and 

 breathing. Another route therefore is opened for 

 the air — namely, through the nose — which lets 

 the breath pass backward and forward, whilst the 

 lips, in the act of sucking, are necessarily shut 

 close upon the body from which the nutriment is 

 drawn. This is a circumstance which always ap- 

 peared to me worthy of notice. The nose would 

 have been necessary, although it had not been 

 the organ of smelling. The making it the seat of 



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