COMMON THINGS MAN. 



prodigious powers of intellect which have been developed in the 

 history of the progress of the human mind. 



75. But even admitting a supposition apparently so impossible, 

 the question of personal identity, which we have referred to 

 above, will raise an insuperable objection to it. Physiologists 

 and anatomists have proved that the matter which composes 

 our bodies is subject to continual change. Every part of our 

 organisation, even to the innermost cores of our bones, is 

 subject to this never-ceasing process of mutation. The food 

 which we take into our stomachs contains, combined with 

 some other matters, all the constituents necessary to compose our 

 bodies. In the process of digestion, those parts which are unsuited 

 to our bodies are rejected, and the several suitable parts passing 

 into the blood, are carried by it through the circulating apparatus 

 to all parts of the system ; to the bones, as well as to the flesh 

 and softer parts ; the peculiar constituents necessary for the 

 maintenance of each part respectively being deposited there in the 

 proper proportion, and the waste carried away. This process of 

 constant renovation and removal of used-up matter of offal, as 

 it were goes on equally throughout the bones as throughout the 

 softer parts. Now, it will be evident that, in such an unceasing 

 process of rejection and renovation, the entire mass of matter 

 composing the body must in a certain period, longer or shorter, 

 undergo a complete change, so that, corporeally speaking, an indi- 

 vidual, at any given period of his life, has not in his entire compo- 

 sition a single material atom which he had at a certain previous 

 period. It was the opinion of former anatomists and physiologists, 

 that the body undergoes this complete change of the matter com- 

 posing it every seven years ; but more recent and exact observations 

 and calculations, founded upon rigorous analysis of the phenomena 

 of digestion, circulation, respiration, and other less important 

 functions, have proved this estimate to err by excess. 



The 116 Ibs. weight of water which forms three-fourths of the 

 matter composing our bodies, is rejected with great rapidity 

 in respiration, transpiration, and natural discharge. The 

 carbon is expired with each action of the lungs in large quan- 

 tities, combined with oxygen, another constituent of our bodies, in 

 the form of carbonic acid. The lime escaping in other ways 

 is rejected from our bones, and replaced by a fresh supply. 

 There is not a movement of the body, whether voluntary or 

 involuntary ; not an action of a member, a muscle, or a nerve ; 

 not a pulsation of the heart or of an artery ; not a peristaltic 

 motion of the intestines, which is not the proximate cause of 

 the rejection of used-up matter and the demand for a fresh 

 supply from the digestive apparatus, just as in a machine the 

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