B I R 



regularity from a flem which h lodged in the neck of the 

 bag. See P/dte lY . Jig. 3. in which tlie purfe of t}\e goi/e 

 is delineated, with its cavity laid open, to exhibit the folds 

 upon the inner furface. 



When more clofely examined, the ftru£lin-e of this part is 

 very curious. Under the peritoneal covering, itisfurroundtd 

 by a very delicate expanfion of mufcle, the fibres of which 

 take a tranfverfe dircftion. The internal tunic of the 

 purfe is made of a thin pellucid membrane, and the folds 

 which have been dcfcribed, confiR entirely of.glandular bo- 

 dies, which are too minute to be diftinguilhcd with the naked 

 eye. By employing a lens of con?.mon magiafying powers, we 

 have dilcovered them to hear a great refcmblancc to the gaf- 

 tric glands, being, like them, little cylinders, which arc per- 

 forated at une extremity to give paffage to their fecreted 

 fluid ; indeed, the only difference which appears between 

 them, is, that the glands of the purfe are fhorter, being 

 fo much comprcffed in feme inllances, that they are nea;!y 

 cf an annular form. Fig. 4. of PJaie IV. exhibits a por- 

 tion of the burfa of the goojl; highly magnified ; a, a, the 

 glands compofing the folds ; />, b, the fpac:s left between 

 the folds, wliich confift only of the tunics of the purfe. 



The fluid produced by thcfe glands, and of which the 

 purfe always contains a greater or lefs quantity, appears to 

 differ in no refpedt from common mucus. Tlie neceffity, 

 however, for fo ample a fupply of mucus, as thefe glands 

 are capable of furnilhing, does not feem very plain, efpe- 

 cially when it is confidered that the purfe of Fabricius is 

 not met with in all birds. Amongfl others, the parrot is 

 without it, asappears by_y?^. I. of Plate IV. in the Anato- 

 my of Birds ; and yet the parrot has a very large cloaca, and 

 might thence be fuppofed to need this glandular apparatus, 

 even more than many birds, admitting its ufe to be the fe- 

 cretion of a mucous fluid, to fheath the cloaca againft the 

 acrimony of the excrement and urine. 



Although the functions of the purfe of Fabricius cannot 

 be dated with certainty, it may be conjefturcd that they are 

 not unimpoitant, from the delicacy of its organization, and 

 its being fo rarely wanting. There are a nuir.ber of black 

 points to be feen within the anus of the parrot, which ap- 

 pear like the orifices of mucous glands : may not thefe fu- 

 perfede the neceffity of the purfe in this bird ? 



The excrements of birds have been afcertained by Vauque- 

 lin and others, to poffcfs an acid. This is increafed by fer- 

 mentation, into which feculent matters rapidly tend, and as 

 it proceeds, the acid gives place to ammonia, which is 

 evolved, towards the end of the procefs, in great abundance. 

 The dung of the pigeon is found to contain an acid of a pecu- 

 liar kind, which is increafed by the mixture of the fxces 

 ■with water. It is from its chemical properties that the dung 

 of pigeons becomes fo ferviceable as a manure, and that it is 

 employed in the procefs of fome manufadUires, and for do- 

 meftic purpofes, fuch as cleanfing clothes, &c. 



Vauquehn has alfo analyfed the fixed parts of the excre- 

 ments of fowls, which being compared with thofe of the food, 

 afforded fome very fingular and important refults. 



For this purpofe he fed a hen for ten days upon oats, of 

 ■which Hie confumcd during that time i i,ii 1,843 gi^'is troy 

 weight ; thefe contained 



136,509 grains of phofphate of lime, 

 219,548 filica. 



B I R 



quantity of excrement ejefled during the tea days contained 

 175,529 grains of phofphate of linne, 58,494 grains of carbo- 

 nateoflime, and 185,266 grains of filica. The amount, 

 therefore, of the fixed parts difcharged from the fyftera dur- 

 ing this period were as follows : 



374,305 grains of phofphate of lime. 



5 1 1 ,9 1 1 grains of carbonate of lime, 



185,266 filica. 



Given out 

 Ttiken in 



971,482 

 356.057 



356,057. 

 ■In the courfe of thefe ten days the hen laid four eggs ; 

 the fhells of which yielded 98,776 grains of phofphate of 

 lime, and 453,417 grains of carbonate of lime. The whole 



SurpU'.s 615,425 



Hence it appears, that the quantity of folid matter parted 

 with by the fyftem during ten days, exceeded the quantity 

 taken in by 615.425 grains. 



The amount of the filica received was 219,548 grains. 



The quantity given out was only 185,466 grains. 



Deficient 34,282 grains. 

 Confequently there difappeared, during ten days, 34,282 

 grains of filica. 



The quantity of phofphate of lime 



taken in was - - 136,509 grains. 



That given out was - - 274,305 grains, 



137.796 



There mufl have been formed, by digeftion in this fowl, 

 no lefs than 137,796 grains of phofphate of hme, as well as 

 511,911 grains of the carbonate of lime. It may thence be 

 prefumed, that hme (and perhaps phofphorus) is net a Am- 

 ple fubllance, but compounded of ingredients which exift in 

 oats, water, and air, which were the only matters that could 

 be introduced into the body of this fowl; as a quantity of fili- 

 ca had difappeared, it might be fuppofed, that it had contri- 

 buted to the formation of the addit'onal produfts ; but if fo, 

 it mufl have entered into combination with a great quantity 

 of fjme other fubifance. See Annal. de Chim. xxix. 16. 



Notwithflanding thefe experiments were conduced by the 

 abieft cliemill of the age, they ought not perhaps to be af- 

 fented to without being repeated under every circumtlance 

 which could lead to the deteftion cf any error that might 

 pofTibly arife. 



This is not only neceffary on account of the extraordi- 

 nary nature of the refults, which could only be produced by 

 a creative power in the alfimilating organs of the animal ; 

 but from other analogous experiments yielding refults of a 

 contrary kind. Dr. Fordyce, for inllance, found that a cer- 

 tain quantity of calcareous matter was required by biids 

 during the period of laying ; and if the bird was deprived of 

 this, the fhtll never was formed, and the bird frequently 

 died from the eggs not coming pr; perly fjrwaid. The me- 

 thod he adopted to prove this was fimple and fatisfaAory : 

 he took a number of canary birds, when about to lay ; fome 

 he inclofed, fo that they could have no accefs to any cal- 

 careous matter ; and to others he gave a piece of old mortar, 

 which they fwallowtd with avidity, and they laid their eggs 

 as ufual ; whilft, on the other hand, tht)fe birds he had not 

 furniihcd with the mortar were unable to produce eggs, 

 and in feveral inflances died. See Fordyce on Digellion, 

 p. 25 & 26. 



Liver. 



This vifcus is fituatcd about the middle of the common 

 cavity of birds. Its form, as in other animals, is much in- 

 fluenced by the ftiape of the parts which are immediately ad- 

 jacent. The left fide lies on the ftomach, the right covers 



the 



