670 PUTREFACTION 



oxygen. The methods actually in use may be called salting, smoking, drying, ex- 

 clusion of air, and parboiling. 



1. The chemical changes of the azotised juices. The substance which in dead animal- 

 matter is first attacked with putridity, and which serves to communicate it to the solid 

 fibrous parts, is albumen, as it exists combined with more or less water in all the animal 

 fluids and soft puts. In those vegetables also which putrefy, it is the albumen 

 probably which first suffers decomposition ; and hence those plants which contain 

 most of that proximate principle are most apt to become putrid, and most resemble in. 

 this respect animal substances. The albumen when dissolved in water, very readily 

 putrefies in a moderately warm air ; but when coagulated, it seems as little liable to 

 putridity as fibrin itself. By this change it throws off the superfluous water, becomes 

 solid, and may then be easily dried. Hence those means which by coagulation make 

 the albumen insoluble, or form with it a new compound, which does not dissolve iq 

 water, but which resists putrefaction, are powerful antiseptics. Whenever the 

 ftlbumen is coagulated, the uncombined water may be easily evaporated, and the 

 residuary solid matter may be readily dried in the air, so as to be rendered unsus- 

 ceptible of decomposition. 



Some acids combine with the albumen, without separating its solution; such 

 is the effect of vinegar, citric acid, tartaric acid, &c. 



Tannin combines with the albuminous and gelatinous parts of animals, and forms 

 insoluble compounds, which resist putrefaction j on which fact the art of tanning is 

 founded. 



Alcohol, oil of turpentine, and some other volatile oils, likewise coagulate albumen, 

 and thereby protect it from putrescence. The most remarkable operation of this kind is 

 exhibited by wood-vinegar, chiefly in consequence of the creosote contained in it, 

 according to the discovery of Keiehenbach. This peculiar substance has so decided 

 a power of coagulating albumen, that even the minute portion of it present in pyro- 

 ligneous vinegar assists in preserving animal parts from putrefaction, when they 

 are simply soaked in it. Thus, also, flesh is cured by wood-smoke. Distilled wood- 

 tar likewise protects animal-matter from change, by the creasote it contains. The 

 pyroligneous acid was said to contain five per cent, of creasote ; it does not do so now. 



The metallic salts operate yet more effectually as antiseptics, because they form with 

 albumen still more intimate combinations. Under this head we class the green and 

 red sulphates of iron, chloride of zinc, the acetate of lead, and corrosive sublimate ; the 

 latter, however, from its poisonous qualities, can be employed only on special occasions. 

 Nitrate of silver, though equally noxious to life, is so antiseptic that a solution 

 containing only s^gth of the salt is capable of preserving animal-matter from corruption. 



2. Abstraction of water. Even in those cases where no separation of the albumen 

 takes place in a coagulated form, or as a solid precipitate, by the operation of a substance 

 foreign to the animal juices, putrefaction cannot go on, any more than other kinds of 

 fermentation, in bodies wholly or in a great measure deprived of their water, as the 

 albumen itself runs much more slowly into putrefaction, when less water is contained 

 in it ; and in the desiccated state it is as little susceptible of alteration as any other dry 

 vegetable- or animal-matter. Hence, the proper drying of an animal substance becomes 

 a universal preventive of putrescence. In this way fruits, herbs, cabbages, fish, and 

 flesh may be preserved from corruption. If the air be not cold and dry enough to 

 cause the evaporation of the fluids before putrescence begins, the organic substance 

 must be dried by artificial means, such as by being exposed in thin slices in properly- 

 constructed air-stoves. At a temperature under 140 F., the albumen dries up without 

 coagulation, and may then be redissolved in cold water, with its valuable properties 

 unaltered. Mere desiccation, indeed, can hardly ever be employed upon flesh. 

 Culinary salt is generally had recourse to, either alone or with the addition of 

 saltpetre or sugar. These alkaline salts abstract water in their solution, and, conse- 

 quently, concentrate the aqueous solution of the albumen ; whence, by converting the 

 simple watery fluid into salt water, which is in general less favourable to the fer- 

 mentation of animal-matter than pure water, and by expelling the air, and probably by 

 chemical combinations, they counteract putridity. On this account salted meat may 

 be dried in the air much more speedily and safely than fresh meat. The drying is 

 promoted by heating the meat merely to such a degree as to consolidate the albumen, 

 and eliminate the superfluous water. 



3. Defect of warmth. As a certain degree of heat is requisite for the vinous 

 fermentation, so is it for the putrefactive. If in a damp atmosphere, or in one saturated 

 with moisture, if the temperature stand at from 70 to 80 F., the putrefaction goes 

 on most rapidly ; but it proceeds languidly at a few degrees above freezing, and is 

 suspended altogether at that point. The mammoths found in the Siberian ice are 

 proofs of the preservative influence of low temperature. In temperate climates, ice- 

 pousos serve the purpose of keeping meat fresh and sweet for any length of time. 





