AND THE LOWER ANIMALS. O 



We see that in the most hidden depths of living 

 beings two contrary currents flow; one, molecule by 

 molecule, constantly removing something from the 

 organism ; the other as rapidly repairing the breaches 

 whiclr, too much widened, would bring on death. At 

 the end of a given period the total, or almost total 

 renewal of the substance of the body, must follow 

 from this double action. 



This is a fact of the greatest importance. In the 

 presence of this instability of the organic components, 

 the decided persistency of form and proportion among 

 living beings can hardly be understood, and the mind 

 is enabled without difficulty to admit the possibility 

 of the most extensive alterations. Truly, we are 

 ignorant of the cause which brings these changes 

 about, determines the order of their succession and 

 includes them within impassable limits; but at all 

 events, we may glance at one of the chief processes 

 which Nature sets at work to create, develop, main- 

 tain, and destroy, under the influence of life. 



