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* hen pafiing over them acquires nearly the thicknefi of an 

 eighth of an inch. Plate II. fig. 2. in the Anatomy of Birds, 

 fhcws the gizzard of the ivihiftvan laid open, d the divided 

 tendon, e the cuticular or horny covering of the gizzard, 

 ending decidedly at the commencement of the inteftine, and 

 below the z me of gaftric glands ; at the latter place the edge 

 is (hewn detached, // the two prominent oval fnrface?, g g 

 the origin of the inteftine, which being cut off fliort on the 

 outfide permits the light to appear through it. 



The cavity of the giz/ard differs verj- much in fhape and 

 extent from what might be expcAcd, from the external 

 figure of that organ. When all foreign matters have been 

 expelled, the two prominent oval furfaces approach each 

 other, leaving only a flit between them : any thing that de- 

 ferves the name of a cavity, is litinted above and below the 

 place where the tendons crofs (fee Plate 11. Jig. 2.^, for juft 

 within the tendon there is not cavity fnfficient to contain the 

 end of a finger. See Plate [II. Jig. I. which fhewsa feclion 

 in which the two oval fnrfaccs are applied to each other, 

 leaving at either end the appearance of a round hole, by 

 means of which the fuperior and inferior cavities of the ven- 

 tricle have communication. 



When the horny or infenfible lining is removed, there ap- 

 pears another coat to the gizzard. This is loft, fomewhat 

 fpongy, and endowed with vafcularity ; it is intimately united 

 to the mufcular fubftance of the vertricle, on one fide, and 

 on the other affords a furface for the adhefioQ of the homy 

 coat ; the connexion with which appears to depend upon the 

 mutual infertion of villous proceffes, too fine to be djllinftly 

 perceived by the naked eye. 



Such is the defcription of the mufcular ventricle, or true 

 glzz-ard, as it exifts in thtfwari, the goofe, the Juci, the phea- 

 fant, and common fowl, the pintado, the turiey, and a few 

 others. In by far the greater number of birds, there is a 

 deviation from the ftruclure of the gizzard. The digaftric 

 mufcle is lefs powerful, its tendon is incoi-porated with the 

 parietes of the ventricle ; the oval, or grinding furfaces are 

 little or not at all diflin ^uifhable from the reft of the cavity, 

 which is therefore of 1 irger capacity ; and, laQly, the fub- 

 ftance lining the ventricle is lefs tough, thick, and hard, 

 aoproaching more to the nature of cuticle. It would be 

 endiefs to enumerate ail the different inftances of intermediate 

 firufture, which we and others have obferved ; fuffice it to 

 fay, that it exifts in almoft all thtpqfferes, or fmall birds which 

 fubfift upon a mixed food, fuch as gram, wonns, infefts, and 

 frj'ts ; alfo in mod; of the order fcanf;res, and in ma:!y of the 

 graUte and anfres, which are purfued as game. In all wkich 

 inftances the deviation from the true flructure of the gizzard 

 varies in degree according to the nature of the food ufed by 

 tlie bird ; nav, differs from this caufe in the fame individual. 

 Thus the gull has a ftrong mufcular ventricle, when fed upon 

 grain, which, if the bird be fupporttd by fiih, becomes fo 

 thin as to approacii the membranous ftomach. 



It is remarkable, that many birds which Kve upon grain 

 and hard fubftances, have neither a very mufcular ventricle, 

 nor the horny integument verj- thick. This is the cafe with 

 all thejlnitbimts birds, and fome gaUina:, as the lujlaid. 



Tlie llomach of the ojlii.h is capacious ; the digaftnc 

 mufcle is thin, confidering the fize of the bird, and the na- 

 * ture of its food ; and the cuticular coat is fo fcft, that it has 

 been aptly compared by feveral authors to flannel. The 

 Parifian anatoraifts defcribe the ftomach of the cajfowary 

 as being thinner than that of the cjlrich, and divided into 

 two Darts by a valvular projeclion of the ini^er coat. 



When the digaftiic mufcle becomes fo thin as to form a 

 mere layer of fibres, in rlofe union with the other coats of. 

 the ftomach, and its tendons only fir.e apoiieuiofes, expnnded 



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on each fide, the ventricle is termed memhrcmous ; an im- 

 proper appellation, inafmuch as the very fame parts e.\ift, 

 which belong to the powerful and maflTy gizzard, although 

 in a difguifed and diminiflied form, and unequal to the fame 

 fundions ; affording thus a curious example of the uniformity 

 with which nature copies her own works. 



This fpecies of ftomach is almoft confined to the aceipitrine, 

 or rapacious birds, and thofe amongft the gralla and anferes, 

 which feed on fifti. The -woodpeckers alfo polTefs it, and pro- 

 bably it may be found in fome foreign birds, which live on 

 infcds and foft fruits. 



The fubftance lining the membranous ftomach is much 

 thicker than common cuticle. It is occafionally foft, at:d 

 almoft of a gelatinous confiftencc, and eafily detached from 

 the internal coat of the ventricle. 



The fliape of this kind of ftomach is iifnally a femi-cval, 

 or the fection of an egg. Several of iht pifcivorous birds, at 

 the heron, bittern, pelican, &c. have, however, a fecond 

 chamber, through which the food pafTes in its way, to the 

 inteftine. See Plate III. in the Anatomy of Birds. Fig. 2. 

 is the ftomach of the heron ; a the lower part of the ccfo- 

 phagiis, appearing fmaller than it really is, .from being 

 thrown into folds ; b the zone of gaftric glands, diftiatllr 

 feen through the coats of the ftomach, in confequence of 

 the cavity being diftended with a tranfparent fluid, and after- 

 wards placed againft the light. If Spallanzani had em- 

 ployed the fame expedient, he conld not have denied the 

 exiftence of a diftinil glandular ftruclure to the heron ; c the 

 inferior part of the ftomach, chiefly compofcd of mufcular 

 fibres,^ fpreading in a radiated manner from the lateral apo- 

 neurofis ; d, which fupplies the place of the great tendons 

 of the digaftric mufcle ; e the fecond ftomach, furniftied 

 with circular mufcular fibres ; / the firft inteftine arifing 

 from the additional ventricle. The communication between 

 the two ftomachs is verj- ftrait in the pelican. 



Having defcribed the ftrufture of the digeftive organ of 

 birds, it remains to confider its funflions. In thofe cafes 

 where the mufcular power of the ftomach is inconfiderable, 

 and the cuticular coat thin and foft, digeftion is carried on 

 in the fame way as in man and other animals, with this dif- 

 ference only, that the gaftric fluid is furnifiied by a diftinft 

 apparatus of glands, inftead of being fccreted by the whole 

 furface of the cavity. In the true gizzard, however, 

 we perceive an extraordinary departure from the common 

 ftrufture of the organs of digeftion. This part fupphes the 

 place of the teeth of other graminivorous animals. In its 

 mechanic powers and aclion it refembles a mill : the upper 

 part ferves as the receptacle for the grain ; the two inttnial 

 projecting oval furfaces correfpond to the mill ftones, and 

 the firft inteftine receives the fubftances in the ground or di- 

 vided ftate. The experiments made tt the acad.-my of Ci- 

 mento, and thofe of Reaumur, Spallanzani, and others, 

 fhew tht.t tlie gizzard is a machine of no ordinary powers. 

 Tliefe experiments confifted in compelling birds to fwailovr 

 liard and unyielding fubftances, and, after fome hours, ex- 

 amining what were the elftdls produced upon them. 



V.'hen balls of glafs, or other brittle fubftances, were em- 

 ployed, they were fpeediiy leduccd to powder : nictals and 

 precious ftones were indented or abraded. Spallanzani in. 

 troduced into the gizzard of the turkey, and common fowl, 

 leaden balls, armed in one inftance Avith twelve (harp needles, 

 one quarter of an inch long ; and in another, fct with as 

 many lancet points. Upon dellroying the birds iS hours 

 afterwards, the needles and lanceti were found broken off, 

 and marks of impreffion appeared even upon tiie balls them 

 felves ; and, what he confidered more extraordinary, the 

 coats of the gizzard were perfeflly ur.Uurt. When we con- 

 ^ li fidef 



