730 



FARMERS' REGISTER-FERMENTATION—PUTREFACTION. 



position presents many stages. Bodies which 

 contain sugar, fUrnish at first" alcohol and carbonic 

 acid, and this stage of fermentation has been cal- 

 led the vinous, or alcoholic. They afterwards 

 become acid, produce acetic acid, which state con- 

 stitutes what is called the acetous lermentation. 

 Finally, the greater part of vegetable substances 

 are changed slowly into mould, (humus) and thus 

 undergo the fermentation called putrid. There 

 are but lew vegetable matters which can pass 

 through these three stages; a greater number com- 

 mence with the second, and a still more numerous 

 class are susceptible of undergoing only the third, 

 that is to say, of entering into putrefiiction. 



[The next positions of the work, wliicli treat at 

 length of vinous and acetous fermentation, are passed 

 over.] 



Putrefaction. 



The last kind of fermentation, or spontaneous 

 alteration of vegetable matters, has been termed 

 putrefaction. The phenomena which it presents, 

 and the pn-oducts which result from it, are much 

 more varied than those of the j)receding fermen- 

 tations; but they have been nmch less examined, 

 and in consequence, are less known. Tlie power- 

 ful vegetable acids, the vegetable alkalis, the re- 

 sins, the fixed and the volatile oils, do not pass 

 into putrefaction: on the contrary, Ijodies which, 

 besides carbon, hydrogen, and oxygen, contain 

 nitrogen and sulphur, putrefy easily. By drying, 

 putrefaction is prevented; and although solid and 

 insoluble bodies may be gradually destroyed in the 

 air, that does not happen when they are com- 

 pletely secured from moisture. Bodies the most 

 putrescent, such as vegetable albumen and glu- 

 ten, are preserved for an indefinite time, after 

 having been dried. Thus a body enters into fer- 

 mentation only as it is filled with moisture. But 

 the presence of water is not sufficient: without 

 oxygen, putrefaction does not take place, or it is 

 so slow that it appears to be stopped. It is upon 

 this circumstance that is founded the method of 

 Appert, of preserving vegetahle matters for a long 

 time. For example, Appert fills completely a 

 glass bottle Avith fresh green ))eas, closes it licr- 

 metically, ties and seals with pitch the stopper, 

 and then places the bottle in a pot of water, which 

 he heats to the boiling point. While thus heated, 

 the peas absorb the oxygen of tlie air contained 

 in the bottle, which is not replaced by the oxygen 

 of the exterior air. The peas are thus preserved 

 without alteration through a whole year. But if 

 the stopper is not perfectly close, air penetrates 

 into the bottle, is renewed, and quickly causes the 

 putrefaction of the peas, which s|tread a tainted 

 odor. By the same means, both animal and ve- 

 getable matters may be preserved. It suffices for 

 that, to place them in vessels closely stopped, and 

 to heat them slowly to 100°, [Cent'igrade.] The 

 oxygen of the air contained in the vessels, is ab- 

 sorbed in consequence of an action winch is the 

 commencement of putrefaction — and the organic 

 matters are then in the midst of an atmosphere of 

 nitrogen gas, and of newly produced carbonic acid 

 gas. Thus air and water are necessary to the 

 production of rapid fiirmcntation; however, their 

 influence is not exerted but with the aid of heat; 

 for under 0°, the temperature at which water 



freezes, organic matters do not undergo any alter- 

 ation. It has been seen that antediluvian animals 

 which had been enclosed in mountains of ice, 

 when exposed finally by thawing, had not under- 

 gone putrefaction, although they had remained at 

 least 6000 years in the ice. Organic matters are 

 preserved sufficiently well even at some degrees 

 above 0°; but from 6° to 7'^, the phenomena of 

 decomposition begin to show, after some time; 

 from 15° to 18° putrelaction is established promptly, 

 and from 20° to 30° it proceeds with great rapidity. 

 When putrefaction is once fully established, it ex- 

 tends very fast, which may induce the belief^, that 

 the products which result from it, have the pro- 

 perty of exciting a reaction similar to that which 

 caused their formation. 



Organic bodies which rot in open air, absorb 

 oxygen; but they rarely retain it; lor ordinarily 

 they disengage a volume of carbonic acid gas 

 equal to that of the oxygen absorbed. When the 

 air does not touch all the points of the bodies 

 which rot, the surfiice of these bodies present phe- 

 nomena difierent from the interior of the mass. 

 At the places where the air is in full contact with 

 the organic matter, every thing is o.xygenated, so 

 that the carbon is converted to carbonic acid, the 

 hydrogen to water, and the nitrogen to nitric acid. 

 But when oxygen is not, or is but slightly in con- 

 tact with the rotting organic matter, the hydrogen 

 combines with the other elements, that is to say, 

 with the carbon, the nitrogen, the sulphur, and the 

 phosphorus. It might be even, that one })art of 

 the hydrogen should be furnished by the decom- 

 position of the water. It is the mixture of these 

 combmations of hydrogen, and their being thrown 

 off into the air, which causes putrefying matters 

 to spread such an offensive odor. Vegetable 

 matters, which contain only carbon, hydrogen, and 

 oxygen, are decomposed without producing a very 

 disagreeable odor; but matters which contain ni- 

 trogen, smell strongly, and when a little sulphur 

 or phosphorus is also contained, the odor of the 

 putrefying body becomes insupportable. As yet, 

 no chennst has set to work to determine with any 

 precision, what are the chemical changes which 

 accompany putrefaction, and what are the pro- 

 perties of (he resulting products. 



If moist vegetable matters are put in a heap, 

 there takes place, especially in hot weather, a re- 

 action between tlieir elements, in consequence of 

 which the temperature is raised; water is disen- 

 gaged under the Ibrm of a thick vapor, and the 

 mass finally becomes heated to that degree that it 

 takes fire and burns. The commencement of this 

 reaction, and its progress to the point of ignition, 

 is certainly a species of putrefiiction; but we are 

 ignorant what are the chemical changes which 

 accompany it, and which make progress rapid 

 enough to cause the mass to be heated to so high 

 a degree. It is the same chemical action to which 

 hay is often subject, when it is put into stacks 

 before having been sufficiently cured; it is heated, 

 exhales a peculiar odor, and would not be long 

 without taking fire, if not opened and dried. 



Organic matters when covered with water rot 

 also, but in so doing, they present other phenom- 

 ena than when they rot in the air. Very often 

 the reaction commences by the production of mi- 

 croscopic animalcules, living and jiossessing pow- 

 ers of motion, which have received the name of 

 infusonj animals. At (he beginning of putrefac- 



