PUTREFACTION. 



Jiftilled over in his experiments, the refidiic, being ftill in 

 inteftine motion, roqnired only the herbaceous imcll. The 

 reafon why thevohitile alkah has been diltindly obferved at 

 a certain period of putrefaflion, and not in the other, he 

 apprehends to be this : the volatile alkali has, it I'ecms, a 

 tendency to difentangle itfelf, by inteftine motion, of all 

 fucli matter as it is involved with ; but if it is not combined 

 with fuch fixed matK-r as retains it till it has gone through all 

 its evolutions, it is, being itfelf volatile, carried off by the 

 ftill more volatile phlogiilic matter with which it is commonly 

 joined. For this reafon, he fuppofes the putrefying matter 

 ihews in its beginning no figns of volatile alkali, becaufe its 

 fmell depends only on thole particles which have been on 

 the furface, without any llrong cohefion with the fubllance. 

 In the farther progrefs of putrefadlion, the matter involving 

 the alkali, or forming it, is intermixed, and in cohefion with 

 the folid particles of the fubftance, and is by thefe means 

 retained till tlie alkali is come to its purer ilate. Towards 

 the end of putrefaclion, the cohefion of the particles being 

 almoft entirety taken of!', tiie volatile alkali is carried off before 

 it can go through all its ftates. 



Dr. Macbride made feveral experiments with putrid blood 

 and putrid bile, which alcevtain the fa<ft, that as foon as an 

 animal fubilance begins to putrefy, it begins to difcover an 

 alkaline quality ; and this volatile matter, now produced in 

 it, may be feparated by diftillation in a very gentle warmth ; 

 but he obferves, that the volatile alkali obtained from pu- 

 trid fubltaiices is not exadtly fimilar to that obtained by 

 violent heat from animal fubftances not putrid. It differs 

 remarkably in the flavour, which is naufeous and difagreeable, 

 is not fo pungent, and is much weaker than the common 

 volatile alkali ; and this latter is capable of difpolielling the 

 putrid alkali, and of driving it off from any body to which 

 it has been united. But to return from this digreflion. As 

 to the caufe and procefs of putrefaftion, it has been generally 

 believed, that the contaft of atmofpherical air is neceflary 

 for this purpofe, and that bodies become putrid, becaufe air 

 communicates fomewhat to them : accordingly it has been 

 alleged, that bodies buried deep under the earth, or in 

 water, out of the reach of any air, have remained entire for 

 ages ; which, when expofed to the open air, have foon 

 rotted and mouldered away. It is alfo well known, that 

 bodies are preferved from putrefadlion by covering them with 

 wax, fuet, &c. ; and Mr. Boyle relates, that he has preferved 

 lemons, oranges, and other fruits, from putrefaftion, during 

 feveral years, by including them in an exhauited receiver. 

 Experiments of the lame kind have been lately made by 

 M. EUer of Berlin, which fhew that fubftances, even of 

 the moft putrefcent nature (fuch as blood) may be kept 

 found in vacuo for many years. But Dr. Macbride has 

 urged a variety of fafts and confiderations to prove, that 

 putrefaftion enfucs in confequence of the lofs of lome prin- 

 ciple, which cemented the conftituent particles of bodies, 

 and that, when this is difengaged from them, they feparatc, 

 and are dilunited. This principle he difcovcrcd to be air, 

 which, in putrefaflion and fermentation, is extricated and 

 thrown off, from a fixed and non-elaftic ftate, into one that 

 is volatile and elaftic ; but which immediately, upon meeting 

 with a proper recipient, returns again to its former nature. 

 Thus he found, that canftic alkali and quicklime may be 

 rendered mild by abforbing this air, extricated from putre- 

 fying and fermenting fubftances ; that without the extrication 

 of this air no putrefailion can happen ; and that even by ab- 

 forption of it, putrefied fubftances may be correfted and 

 rendered fweet. To the fame purpofe Dr. Alexander has 

 endeavoured to prove, that putrid matter will preferve other 

 fubftances from putrefaAion ; which is not improbable, be- 



caufe, being already faturatcd with the putrid effluvium, 

 they cannot readily ta.ke any more. Dr. Macbride, having 

 expofed putrid matters to the vapours arifing from ferment- 

 ing mixtures, or from alkaline fubftances etfervefcing with 

 acids, found that the putrid quality was deftroyed ; and 

 hence he confiders the fixed air as powerfully antifeptic. 

 And it appears alfo from the experiments of Dr. Prieftley, 

 that fixed air correfts and renders wholefome air tainted with 

 refpiration or putrefaftion. Hence he infers, that hme-kilns, 

 which difcharge great quantities of this air, may be wholefome 

 in the neighbourhood of populous towns, the atmofphere of 

 which mult abound with putrid effluvia. Sir William Lee, in 

 a hot feafon, contrived, by impregnating water with fixed air, 

 in the manner defcribed under PvkmoM' ■zi/^^fr, and waftiing 

 meat with it two or three times a-day, not only to preferve 

 it as perfectly fweet and good to the extent of ten days, as 

 at the firft killing, but alfo to recover fome meat that had 

 begun to change. And it is farther well known, that fixed 

 air, or carbonic acid, has been lately introduced into the materia 

 medica, and adminiftered with fuccefs in a variety cf putrid 

 cafes. Dr. Macbride has alfo proved, that putrefaction is 

 accelerated by taking off the prcilure of the atmofphere ; 

 and from lome experiments he was led to conclude, that it will 

 take place fooner in vacuo than in the open air ; but making 

 a more complete vacuum by means of two brafs hemifpheres 

 joined together, he found that the obfervation of Mr. Boyle 

 and others was agreeable to fa£l. It appeared alfo, by in- 

 clofing flefh in condenfed air, that increafing the preffure 

 of the furrounded air, retarded putrefaction ; and hence he 

 deduces, what he deems to be a demonftrative proof, that 

 bodies do not putrefy, becaufe the air adds fomewhat to 

 them ; for if they did, then a piece of flefti which lay in 

 condenfed air ought to have putrefied the fooneft, becaufe it 

 had the greateft quantity of air applied to its furface. But 

 the reafon why, according to his lyftem, condenfed air pre- 

 vents putrefaction is, that the preffure of every fide muft force 

 the conftituent particles clofer together, thus increafe their 

 cohefion, and prevent the inteftine motion ; and without 

 inteftine motion there can be no change of combination. 

 However, it is obferved by fir John Pringle, that the putre- 

 fadtion of meat and other fubftances, advances quicker in a 

 confined than free air ; for as the moft putrid parts are alfo 

 the molt fugitive, they inceliantly iflue from a corruptible 

 fubftance, and difperfe with the wind ; but in a Itagnation 

 of air they remain about the body, and in the nature of a 

 ferment excite its corruption. 



It has been long obferved, that putrefaftion generates air. 

 Hence, though fleffi, as well as blood, be fpecifically hea- 

 vier than water, yet dead bodies are found to float, after 

 lying fome time at the bottom, from air generated in the 

 bowels by putrefaction. And fince it has been found by 

 experiments, that the blood and other animal fubftances 

 begin to emit air before they are fo far corrupted, as they 

 frequently are in putrid difeafes, it is probable that feveral 

 of the fymptoms in deep furfeits may be owing to the adtion 

 of the confined air. As dead bodies become putrid from 

 the lofs of their fixed air, according to Dr. Macbride's 

 theory, he fuggefts, that the immediate caufe of putrefadtion 

 in living bodies may be the detachment of too large a pro- 

 portion of their fixed air. This fadt he endeavours to evince 

 by an enumeration of the fymptoms that occur in the fcurvy, 

 and other highly putrid difeafes, which ihew that the air 

 is adtually detached from the blood in fuch cafes ; as well 

 as from an examination of the principal and prevailing caufes 

 of fuch diforders. And fince the air tainted with animal or 

 vegetable putrefadtion is the fame with air rendered noxious 

 by animal refpiration ; fince both equally estinguilh flame. 



