44 Mayow 



nitro-aerial spirit. Should any one be inclined to 

 think that the fermentation of the said liquids 

 ought not to be classed among effervescences with 

 a destructive tendency, I reply that although the 

 juices expressed from plants become more perfect 

 by fermentation so far as their use to man is con- 

 cerned, yet, in respect to the compound whose 

 structure it impairs, the aforesaid effervescence is 

 rightly called destructive. 



But when the decay of things is caused by extran- 

 eous heat and moisture, the internal movement is 

 mainly effected by nitro-aerial particles supplied by 

 the air. For nitro-aerial particles abound in a moist 

 warmth ; for we must suppose that heat of all kinds 

 is due to their motion.^ When therefore nitro-aerial 

 particles enter any substance along with extraneous 

 moisture, they engage in conflict with the saline- 

 sulphureous particles which they meet, and in con- 

 sequence of their mutual agitation the structure of 

 the compound is dissolved. Hence such things as 

 exclude nitro-aerial spirit protect substances from 

 corruption. And this is the reason why vegetable 

 fruits, and even flesh, when covered with butter are 

 preserved for a long time from putrefying, also iron 

 smeared with oil is not corroded by rust. And 

 indeed oil and other things containing sulphur 

 appear to be extremely well adapted for excluding 

 nitro-aerial spirit. For sulphureous and nitro-aerial 

 particles, from their mutual enmity, keep off and 

 repel each other, as I have attempted to show in 

 another place ; and for a similar reason, spices which 

 are full of sulphur keep dead bodies for a long time 

 from putrefying. 



It is an additional proof of the foregoing that 

 those things which consist of a combination of 



