THE SMITHSONIAN INSTITUTION. 145 



to grow and strengthen until at length it extends its blighting influ- 

 ence over the entire character. But tliough there be this resemblance 

 in the commencement and progress of the two cases, there is a wide 

 differen.ce in the results. In the first instance it is only the corrosion 

 of a cottnparatively worthless price of metal ; in the second, it is the 

 wasting, the blackening, the ruin of a human soul. 



The alterations which organic bodies undergo, when no longer per- 

 vaded by the principle of life, are due to the attacks of oxygen, di- 

 rected still through the medium of water. In themselves they have 

 no tendency to change. The first movement among their atoms is 

 always impressed from without. It is the interposition of new affini- 

 ties that breaks up the existing combinations and determines a re- 

 arrangement of the particles. The most delicate viands, hermetically 

 sealed in canisters from which the air has been removed, may go 

 round the world unaltered. Fruits hermetically sealed in their skins 

 are in like manner preserved from decay. When the skin is broken 

 or has become so changed in texture as to admit the air, decay at once 

 commences. Timber sunk in mud or water to so great a depth as to 

 be beyond the reach of oxygen, will remain unchanged for centuries. 

 The preservative powers of alcohol do not depend simply upon its co- 

 agulating the albuminous constituents of the animal and vegetable 

 tissues, and depriving them of a portion of their water ; it shields the 

 substances buried in it from the attacks of oxygen. Phosphorus, 

 which soon blackens in water from superficial oxydation, undergoes 

 no change in alcohol. In water the protoxide of iron soon runs into 

 the peroxide. In alcohol, it remains unaltered. Turpentine and 

 most oT the essential oils owe their preservative qualities in a great 

 jneasure to the exclusion of oxygen. The salts, bitumen, and aro- 

 matic gums employed by the ancient Egyptians in embalming, were 

 not simply of service in drying and hardening the animal tissues — 

 their chief use was in shutting out the oxygen. Whatever docs this 

 renders the bodies most liable to decay incorruptible. 



As in the case of the metals, the thinner the stratum of the water 

 interposed between organic substances and the surrounding atmo- 

 sphere, the more rapidly is the oxygen transferred to them. Hence 

 wood, hay, straw, and the fibres of cotton decay faster if simply 

 wetted, than if wholly immersed in water. Some of these when in 

 large quantities and j)ervaded by a dile degree of moisture, become so 

 heated in the interior of the mass as to pass from the ordinary to the 

 extraordinary mode of oxydation, thus furnishing an instance of 

 what is called spontaneous combustion. Vegetable mould and the 

 organic constituents of manures decompose more rapidly in a sandy 

 soil which allows the water to percolate it freely, than in a clayey 

 soil which retains the water. One of the chief benefits of drainage 

 consists in the freer admission of the air to all parts of the soil. The 

 organic matters contained in it are more rapidly oxydized and con- 

 verted into food for plants. If to alcohol, so far diluted as to admit 

 the air among its particles, there be added some vegetable ferment, it 

 will pass, by oxydation, into acetic acid and water. Many weeks, or 

 even months, however, may be required for completing the transform- 

 ation. But if the same mixed fluid be brought in contact with the 

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