B t R 



B I R 



jial furface. The Foramina of tlie cervical vertebra Lave com 

 inuiiicatlo'i with tiit- lateral air-cells of tile neck. 



The air-ho'.es o; tlie anterior ribs are placed upon the 

 ends of thefe bones, where they art joined to the iJcrnum. 

 Tliey arc fnpplicd from the inttrnudiate ai'd lalcial thoracic 



to any one pi:rpofe, and fnfpefted they m'ght be ufeful in 

 giving tone and Itrength to the fong ot birds. 



The oblervations of tlie acddemicians appear to us per- 

 fedily fatisfactorv' with leipect to theconntCtion between the 

 exiftence of the air-c lis, and the oihce of the lungs. They 



P/jl( \ I. in tiie j4na/omy of Birds. Ji^. 5. dddd have related, that during the aft nf infpiration the ftcrnum 



refer to the opening upon the denial ribs. was elevated, and the thoracic air-cells diitended at the fame 



The air paiTes into the pofterio'- or verti brnl ribs by a niim- moment with the lungs, and tliat when the air was ExptUcd 



bei' of foramina, fituated upon the internal furfacc of their from the lungs and thoracic ceils, by the dcprefTion of the 



extremities next the fpine. Thefe foramina appear to have ftenium, one portion ot it was cxpTcd by the trachea ia the 



from their fituation a direft communication with the poftc- ufual way, and the reil was urged into tlit cells of the abdo- 



rior furface of the kmgs. See Plat: VI. in the j^iiatomy of men, ll e two parts of the cavity thu^ becoming alternately 



Birds. Fig. 7. is a vertebral rib of the y?!;r/" leen upo'i its enlarged and diminiflied. In order to akcrtain with the 



inner fide, a the procefs which articulates with the bodies more certainty the condition of the air-cells during re- 



of the dorfal vcrtcbrx, b the part joined to the tranfverfe fpiration, the academiciaiis lubjcfted fcvtral large birds, fuch 



proceffes, c c the feveral air-holes. as the /r/r/rv, ^0^, &c. to the experiment of having the 



The air-holes of the bones of the pelvis are fo numerous, parietts of tlie belly dilfeftcd off without injuring the air-cells, 

 and occur with fo much irregularity, that they do not ad- while the animal was ftill alive, by whitb they had an oppor- 

 niit of a particular defcription. They are all lituated upon tunity of obferving, that the air-ctUs below the fternum were 

 the internal furface of the bones, and appear to be confined rendered teufe during the time the thorax was dim-nifhcd for 

 to that fpace covered by the kidnies, under which tlie air exipiration, and that as loon as tlie ilernum was railed to in- 

 mad infir.uate itfelf from the abdominal cells, in oidcr to creafe the capacity of the thorax, the abdominal air-bags 

 reach them. become fl.iccid. We have made an experiment of a fimilar 



The palTrige of the air into the femur of the ea^k and kind, with the fame refult ; the abdomen of a living goofe 

 Jlork is through an opening upon the fore part of the vvas laid open, from which no air proceeded during infpira- 

 bone, juft within the proceis correfponding to the great tioii, but while the air was dilchnrged from the lungs, it paffed 

 trochanter. It is a round deprcnion, under the edge ot into the abdcminal cells and through the opening of the 

 which the anertures leading to .the cavity of the bone are belly with fo much foice as to blow out a candle. The 

 fituated. See. Plate W. TinA Jig. 't^. i^i iW Anatomy of Birds, neccfiity of having the cavity filled w!ih air in birds, oh- 

 which reprefents the femur of the eagle feen upon the ante, vioufly arifcs from the circuinllancc of tiie lungs being con- 

 rior fide ; a the air hole, bb the cavity of the bone laid open, fined to the pollerior part of the thorax, and confequently 

 exhibiting a number of olTeous procefTes, pafling in all direc- not capable of fuffering any compreffion from the contrac- 

 tions, dividhig the bone on the infide into many irregular tion of the cheft, but by the interpofition of lome other 

 cells ; thef^e are moll numerous towards the extremities of the parts. 



femur, and are hardly to be feen in the centre ; c an artery 

 dillributing its branches to the membrane which lines tl'.e in- 

 ternal part of the bone. The air-hole of the femur in thefe 

 birds communicates with the gluteal cells. 



In thc_/i'/'w//j/«/j' birds the air-holes ot the femur are placed 

 upon the pofterior part, and are found upon both the upper 

 and lover portions of the bone. See Plate VI. in the yJna- 



Many have fuppofed that the air-cells were rot only 

 mechanically fubfervieiit to the actions of rcfpiiatiou, but 

 anfwered another important purpofe by collecting a quantity 

 of air, which in repailmg the lungs tfFcdted a further change 

 upon the blood, tiius noducing a fort of double refpiration ; 

 but the free communication wl:ich cxills between the lu"gs 

 and the cells, renders it probable that the air on its return 



tomy of Birds. Fig.g. fhews the potterior furface of thefe- palfes direCtly by the air-holes into the branches of the 



mwT oi z young qjirich ; « a dcpreiiion on the upper part of bronchiae, and, confequently, is never brought into contact 



the bone, containing a number of air-holes, b the inferior with the blood. It would therefore appear that the only 



depreffion with only three foramina. pait the cells oerform in the procefs of relpiration is to fup- 



The air-holes of the lov/er jaw have been obferved in the ply an elallic medium, by mea.is of which the motion of the 



African and New Holland oftrichcs, x\\t Jlork, the b::ceros na- fternum and ribs, equally a;:d regularly afi"ec1 every part o£ 



Juius z\tA luceros rhinnceros, and the croiw ; and in all thefe the lungs, 



they confilt of two holes fituated upon the two extremities The air-cells making part of the mechanifra of the 



of the jaw bchiid the articulation. See Plate VI. in the 

 Anat'jmy of Birds. Fig. 10. is the lower iaw of the cr.jtii ; 

 aa the two air-holes. Thefe foramina communicate by a 

 tube with the cavity of the car. 



The air does not penetrate the bones of the head and 

 jaws in lualer fowls, 



organs of rtfpiration, does not preclude them, from anfwcrinir 

 other purpofes in the animal economy, it is pi?.m to de- 

 monllration that the bodies of birds lofe much of their rela- 

 tive weiglit by containing air in tl.cir cavities, and llill more 

 from its admiffion into the external parts and the bones ; the 

 advantages of which in tranfpoiti.ig- themfclves through fo 



Having deicribed th.c diftribution of air, which takes hght a medium as the air, or even ia locomotion upon a lolid. 

 place throughout the bodies of birds, it remains to jtiTign an furface, are too obvious to be infilled upon, 

 ufe to this moil carious and peculiar circum.dancc in their The air while it remains in the body, neccffarily acquires 

 anatomy. It has been already ftated, that the opinions of the temperature of the living bird, which renders it much 

 anatomifls upon this fubjeA are diiTerent. The members of lighter even than atmofpheriu air, and tlierefore it ads like 

 tiie French academy fuppofed that the air-cells were uecef- that contained in the fwimming bladder ot fiilits. 

 fa.-y to carry on the actions of refpiiation in birds. Cam- A comparifou of the llructnre cf one bird with another, 

 per thougiit that air was admitted into the bodies of birds proves that the quantity of air is in proportion to the ra- 

 for the purpofe cf dim.inilhing their gravity in relation to pidity and continuance ot the animal's motion, all other cir- 

 their bulk, and thus facilitate their motions ; while Mr, cumftances being the fame ; and that tiie air is diilributed 

 Hunter, the greatefl phyfiologill of this or any other couu- always in preference to thofe members which are mcll em- 

 try, felt unwilling to confine the fundlioas of the air cells ployed in locomotion, as ha? been already pciiited out. 



Ife 



