126 NUTRITION. 



carried out of the system, and* new ones are deposited 

 to supply their place. 



Emily. Amidst such a multitude of operations, how 

 is it possible that no clashing, no interference should 

 take place that the system should not be destroyed by 

 the action of its own organs ! 



Dr. B. See too, amidst all this simultaneous reno- 

 vation and decay, how admirably the forms and beauty 

 of the organs are- preserved ! Even the most delicate 

 lineaments of the face, and that intelligent lustre of the 

 eye, which are recognized by all, but defy the power of 

 the master-artist to embody on the canvass or the mar- 

 ble, are retained with striking distinctness through the 

 various stages of life. 



Emily. Can you inform me how long any particle 

 continues a constituent portion of the body ? If they 

 are constantly changing in this manner from birth till 

 death, why certainly at different periods of life, we must 

 be very different persons, and we may justly I ihink, 

 apprehend the loss of our personal identity. 



Dr. B. Physiologists, I believe, have never yet 

 been able to find an answer to your question. Howev- 

 er, you have nothing to fear on the score of your per- 

 sonal identity, for this consists not so much in the mat- 

 ter which composes our bodies, as in the forms which it 

 assumes, and the spirit by which it is actuated. 



Emily. Does riot the activity of nutrition vary in the 

 different periods of life ? It seems rational to suppose 

 that it would correspond with the energy of the consti- 

 tution generally. 



Dr. B. Your conjecture is correct ; nutrition enjoys 

 its greatest activity in infancy and childhood, when the 

 body is not only to be nourished simply, but increased 

 and' developed. It is then that the features are most 

 liable to alteration ; that wounds are more readily healed; 

 and fractures otbe bones most speedily united. 



Emily. At what precise period in all the varied op- 

 Aerations to which the food is subjected, does it undergo. 



