LETTER I. 



3 



us is ; and has as real a personality as belongs to our 

 mare Fanny or our dog Ccesar. 



5. Nor is this all. They proceed also on the prin- 

 ciple, that however the appointed term of life and size 

 of organism may vary in the different sorts and species, 

 all living beings without exception are subject to the 

 law both of a determinate duration of life, and of a 

 determinate size of organism. 



6. And this principle is unquestionably a sound one. 

 No law of nature is more absolute or universal than 

 the law of mortaUty. Everything that hves, be it 

 plant or animal, lives only for a given time, on the 

 expiry of which it passes into the state or condition of 

 death. Nor is this left to be brought about by acci- 

 dental causes. To these, indeed, it is often owing, 

 the greater number — probably of all sorts — of living 

 beings thus prematurely perishing. But independently 

 of such causes, the loss of its vital properties, and the 

 cessation of its vital actions, is a fundamental law of 

 the constitution of every living being. The conditions 

 of its existence include within themselves provisions 

 for its dissolution. The arrangements to which it 

 owed its origin, and by which its vital actions have 

 been since performed, are such as unfailingly ensure 

 after a time the extinction of its vital powers, — 



" Naseentes morimur, finisque ab origine pendet."^ 



Such changes are gradually wrought in it by the 



