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conduces to health, and what to a long life ; for some things, 

 though they exhilarate the spirits, strengthen the faculties, and 

 prevent diseases, are yet destructive to life, and, without sick- 

 ness, bring on a wasting old age ; whilst there are others which 

 prolong life and prevent decay, though not to be used without 

 danger to health ; so that, when employed for the prolongation 

 of life, such inconveniences must be guarded against, as might 

 otherwise happen upon using them. 



Things seem to us preservable either in their own substance 

 or by repair ; in their own substance, as a fly, or an ant, in amber ; 

 a flower, an apple, etc., in conservatories of snow ; or a corps of 

 balsam ; by repair, as in flame and mechanic engines. He 

 who attempts to prolong life, must practise both these methods 

 together; for separate, their force is less. The human body 

 must be preserved as bodies inanimate are ; again, as flame ; 

 and, lastly, in some measure as machines are preserved. There 

 are, therefore, three intentions for the prolongation of life ; viz., 

 i. to hinder waste ; 2. secure a good repair ; and 3. to renew what 

 begins to decay. I. Waste is caused by two depredations ; viz., 

 that of the internal spirit, and that of the external air ; and both 

 are prevented two ways; viz., by making these agents less 

 predatory, or the patients, that is the juices of the body, less apt 

 to be preyed on. The spirit is rendered less predatory, if 

 either its substance be condensed ; as, i. by the use of opiates, 

 preparations of nitre, and in contristration ; or, 2. if it be less- 

 ened in quantity, as by fasting and diet ; and 3. if it be mod- 

 erated in its motion, as by rest and quiet. The ambient air 

 becomes less predatory, either when it is less heated by the sun, 

 as in the cold countries, caves, hills ; or kept from the body, as 

 by close skins, the plumage of birds, and the use of oil and 

 unguents, without spices. The juices of the body are rendered 

 less subject to be preyed on, if made more hardy, or more 

 oleaginous, as by a rough astringent diet, living in the cold, 

 robust exercises, the use of certain mineral baths, sweet things, 

 and abstaining from such as are salt or acid ; but especially by 

 means of such drinks as consist of subtile parts, yet without 

 acrimony or tartness. II. Repair is procured by nourishment, 

 and nourishment is promoted four ways: I. by forwarding in- 

 ternal concoction, which drives forth the nourishment, as by 

 medicines that invigorate the principal viscera ; 2. by exciting 

 the external parts to attract the nourishment, as by exercise, 



