A B S 



to' '5, as wcU for fomc time after t'-.-y nrc 



K-f- the life of them. Dr. CuUcn (Mat. 



Mel. vol. li. p. 411;.) obfor\cs that chalk, and the few.al 

 t-llac^'3. may lie lufely uf^J for corroftiiic; acidities of thj 

 prim;? viar, in lar.,'e qinncitits ; ar.d fays that if, upon being 

 ioined with the acid of the llomach they become allringent, 

 It is an eflfecl whicli he has not obfcVved, and which, if it 

 CT.T happen, mull rarely occur. Tlieir utility in dianlio:a 

 h? afcribes, not to their allnngent quality, but merely to 

 their corrcfting acidity, which, by beir.g mixed with 

 the biK", had occalloned' the difcafe. Burnt hartdiorn he 

 fays 13 the weakell of all the abfoibent^ ; and he thinks it 

 has nut any pecidiar virtues. Van Swietcn, ki his Commen- 

 taries on B:}eihaive'3 Aphonfms, obfcrves, that thefe ab- 

 forbent powders ought not to be ground too fine, but rather 

 left fomewhat coark-, as tliey will be Itfs apt to concrete 

 and pix)ve dangerous. The college of Berlin, however, fen- 

 fible of the advantage of having the earths, when adminif- 

 tered in febrile cafes, previoufly dilTolved, or reduced to a 

 foluble faline form, direcls them to be digelled in diftilled 

 vincpjar with a gentle heat, till the menftruum ceafes to acl, 

 and the fdtered folution to be infpilTated to drynefs. This 

 preparation, fays Dr. Lewis, is greatly preferable to the 

 fimple imbibition with vinegar or lemon-juice recommended 

 by fome ; as by this laft management the earth is made foh.i- 

 hle only in part, and in an undeterminable proportion. Ab- 

 fovbents are fometimes applied to ulcers ; but it is to be ob- 

 fer\ed, that the inlipid terrcllreous abforbents, fuch as 

 coral, &c. put inro an ulcer, wliere a bone is carious, can 

 have little effecl befidcs that of imbibing the matter of the 

 ulcer: if they fall into any laTifrawAtof the corruptedbone, they 

 may remain fo lo-ig there, that tlie matter imbibed by them 

 may become acrid. Lint is an abforbent, which has not 

 this difadvantage. See Monro in Med. EiT. Edinb. vol. 

 V. art. 24. 



Experiments h?.ve been made for determining the compa- 

 rative ftrength of different abforbents, or the quantities of 

 acid they are capable of fatiating. Langius (Op. Med. 

 Lipf. 17C4, p. 452.) reports, that 10 grains of crabs-claws 

 dcltroyed the acidity of 40 drops of fpirit of fait ; that egg- 

 fhells, crabs-eyes, and mother-of-pearl, taken in the fame 

 quantity, faturated 50 drops each ; red coral, white coral, 

 and fixed a'kaline Talt, 60 drops each ; volatile alkaline fait 

 and pearl, 80 drops each; chalk, 100 drops; oyfter-fliells, 

 120; and fome lirne-ftones, 160. Thefe experiments can- 

 not be much relied on, as earths have different habitudes 

 to different acids. Accordingly Romberg concludes from 

 his experiments, (Mem. Acad. Royal, des oc.de Paris pt)".r 

 I'ann. 1700,) that oyfter-fisells require for their folution 

 more of the marine acid t'lan coral does ; whereas the cafe 

 is the revcrfe with the nitrous acid. But neither of thefe 

 acids is that which abforbents are dcfigned for fatiatii'.:; in 

 the human ftomach. The vegetable acids, and the acid of 

 milk, arc moll analogous to thofe which are jfenerated in 

 the animal body ; and on trying thefe wiih tlie feveral fub- 

 ftmces above enumerated, the differences in their abforbeut 

 powers appeared not to be very great. Lewis Mat. Med. 

 645. 



ABSORBING, the aft of fucking up, or imbibing an- 

 other body. Sir Ifaac Newton fliews that black bodies ab- 

 foib all the rays they receive, and that thofe rays of light 

 which impinge againft the folid particles of bodies are ab- 

 forbed and loft : but it appears from fome later experiments 

 and obfervations of M. Bougv.er, that this effeft is to be at- 

 tributed, not to the impaft of light on the folid parts of 

 bodies, but to the action of fome power diffufed over their 

 furfaces. He found by repeated trials on the refleftion of 



the 



e 



A B S 



light, from the furface of water, and of different pieces of 

 crvllal, tli.it a confiderable q'lantity of light, when the 

 angle.; of incidence were fmall, was actually extuiguilheJ 

 This efftjd, he obfervcd, was dlminiibed by increafmg th( 

 incidence ; fo that at an inclination to cryltal of above 

 49" 49', a very fniallpart of the rays was abforbed ; though 

 fome few were loll, when they fell perpendicularly on 

 the refleding furface. Sec his Traite d' Optique. Paris 

 1760. 



ABSORPTION, in xWAnimnl Economy, is the funftion 

 performed bv the Absorbent veffels above defcribed. The on- 

 ly opportunity which anatomift-^ iiave hitherto met with of ob- 

 fervin^f the orifices of th.efe veflch, is upon the villou;; coat of 

 the inteftines. The accounts which have been given of them 

 in that filuation are fo varioits, and delivered with fuch little 

 confidence as not to warrant the infertion of any defcription. 

 The internal coat of the inteftine is feen fpeckled with chyle 

 coagulated in the mouths of thefe veffels, in perfons who 

 have died when the abforption of that fluid was can7ing on. 

 The evident reluclance with which the abforbents admit 

 noxious matter has led to the genei-al belief, that tlieir 

 mouths are iiTitable, and have the power of denying admif- 

 fion to ftimulating fubftances. Various theories have been 

 formed to account for the admiffion of matter into the ori- 

 fices of the abforbing \cfrcls ; but whichfoevcr theory be 

 adopted, it is previoufly neceffary to admit a correfponding 

 aprtude in the vefiel to receive, and in the matter to be re- 

 ceived. This being granted, fome phyfiologifls have ima- 

 gined that the abforbeat attracted matter into its mouth, in 

 the fame manner that capillary tubes imbibe fluids. A little 

 refleftion is fufficient to fhew that the abforbing vefTcls are 

 not circumftanced hke capillar)' tubes (the fides of which 

 are rigid) imm.erfed in a fluid. Befides, were fuch attrac- 

 tion the caufe of abforption, that procefs fhould be carried 

 on with regularity. On the contrary, abforption is occa- 

 fionally very deficient when an abundance of fluids, as in 

 oedema, is prefented to the mouths of the veffels. This faft 

 may indeed be explained by fuppofing the orifices of the 

 veffels to be in a contrafted ftate, but the contrary problem 

 is more difficult of folution. In the courfe of one night a 

 pint of pus mav be imbibed from the cavity of an abfcefs, 

 and fometimes abforption is fo exceffive that the very fub- 

 ftance of the body is in parts removed, and chafms in con- 

 fequence created. 



Other phyfiologifls have endeavoured to difcover fome 

 propelling power which fhould protrude the matter fubjecl 

 to abforption into the moutlis of thefe veffels. The pref- 

 fure of th; atmofphere on the furface of the body has been 

 confidered adequate to this effect, and the depofition of 

 new matter by the fecerning artery has been affigned as the 

 caufe of the propulfion of the old particles into the orifice of 

 the abforbent. Were this theory correct, fecretion and ab- 

 forption fhould more exactly coiTefpond than they are 

 known to do ; like the former theon', it appears inadequate 

 to account for the fafts above flated. 



Mr. John Hunter who contemplated the fails of natural 

 and morbid abforption in animal bodies with the mofl fleady 

 attention, acknowledged that he was unable to account for 

 the effefts produced, unlefs by attributing to the mouths of 

 thefe veffels powers fimilar to thofe which a caterpillar exerts 

 when feeding upon a leaf. This idea, however, has gene- 

 rally been confidered as too wild and chimerical. 



Doftor Fullarton, in his ingenious Thefis on abforption, 

 published at Glafgow in 1800, attributes to the abforbing 

 orifices a power of fuftion, which opinion he fupports not 

 only by arguments but by analogies. The umbilical tube 

 of the embryons of the fepias and polypi is faid, on the au- 

 thority 



