B I R 



B 1 R 



TTie tendinous cords, however, which are attached to the thofc which belong to the ftcrnum, and terminated in the 



margins of the valve, are not moved by dillind mufcular aponeurofis which covered the lungs. Mr. Ranby difcovercd 



fafciculi, or earner columnit, but proceed immediately to be eiglit mufcular fafciculi to each lung of the ojirich. See Phil, 



loft in tlie fidi.-8 of the ventricle. The lower part of the Tranf. N^ 386. p. 223. We have noticed only t'Hir broad 



cavity is fafciculated, alihoHa,h not fo rcmaikaLly as the in- thin flips of mufcle in the goofe, which proceed from the arti- 



tcrnal fiirf.ce of the ventricle of man or quadrupeds. cu'ation of as many vertebral ribs with the fternal ; in tlic 



The aortic or femicirculai' valves are to be found at the common fowl, the mufclts of the lungs do not prefent 



oriyin of the !;reat arterial trunk from the I It ventiicle. the appearance of diltinct flips, as in other inltanceS) but arc 



Thf above account of the mtchanifm of the heart of birds fprcad as a fingle layer upon each hmg. 

 (hews that this orjran is calculated to exercife its functions It is diScult to fpeak with certainty of the ufes of the 



prccifely in the fame manner in thefe animals as in mammalia; pulmonary mufcles. The effect of their contraction appears 



and that the pulmonary and general circulations are main- to be the tenliou of the aponturofis, and confequently the 



tained by different chambers of the heart; confequently elevation of it into a flat furface which is ordinarily concave or 



■tvery particle of blood is expofed to the influence of the air dcpreffcd. This would neccffanly produce feme dilatation 



in the lungs, previous to its diftribution throughout the fyf- of the lungs ; and therefore thcle mufcles might be reckoned 



tcm for the purpofes of nutrition, excretion, S:c. Before amomr.l the agents of infpiralion, although their operation 



the dcfcription of the vcflels of general circulation is entered in this way would be very trifling. 



upon, it is in order therefore to treat of the organs of rtfpi- The Parilian anatomills attributed fev<ral ufes to them ; 



ration, or the they fuppofed that thefe mufcks had the power of dtprtffing 



J^ungs. the anterior part of the thorax, in confequence cf their at- 



Thefe bodies are fituatcd on each fide of the dorfal fpine, tachment to the moveable angle of the nbs, and their ob- 



upon the fnrface of the ribs and intcrcoftal fpaces, ufuallr lique courfe upward to the fpine. If tliey be allowed to 



reaching in length from the fecond rib to the laft iutercoftal perform this effect, they muft be conCdered as mufcles of cx- 



fpace but one, and extending in breadth from the fpine to piratlon. 



about that part of the ribs, where the proceffes are fent They imagined alfo that they caufcd, when in aftion, a 



from one to the other. In the ojlnch, the lungs were found conftriction of the forair.ina through which the air is ad- 



to meafure ten inches long, and three and an hr.lf broad, niittcd into the great air-celis of the thorax or upper part 



of the body, and thus enabled the bird to maintain a con- 

 tmued diltenfion of thefe cells, in order to diminilh the 

 fpeciHc gravity of its body during the time it remained on 

 wing ; or (what the academicians thought more probable) 

 furnilhed the bird with a fupply of common air to carry 

 figure polferiorly exattly correfponds with that of the parts with it into the regions of the atmofphere, in which the 

 upon which they are laid. The ribs and intcrcoifal fpaces ferve air would be too thin and light for refpiration ; in the laft 



and were one inch and an half in thicknels. 



The lungs of birds never move from their pofition, as they 

 adhere to the inlide of the cheft, and are covered over by a 

 llrong membiane or aponeurolls. 



They are fmooth and even on the anterior part ; but thci: 



as a mould, of which the lungs are the perftcl calf, prefent- 

 ing a remarkable prt j^-ction for each depreffion between che 

 ribs. Thcie eminences are of courle moll ftriking next tiie 

 fpine ; and towards the anterior edge of the lung';, which is 

 *ery thiu, they are fcarccly vilible. 



The lungs have two coverings ; one is fomewiiat analor 

 gous to the pleura, though not exactly iimilar to it in ftnic- 



conjecfure, however, they fecm to have forgotten the effeft 

 that the temperature of the bird's body would produce ia 

 the rarefaftion of the air contained in the cells. 



When the lungs of birds are ilripped of their coverings, 

 there are llill found to be a connected, uniform fublfancc, 

 and not reducible into lobes or lobules as in mammalia ; thejr 

 appear, to a fupeihcial view, folid and flefliy, but if ex- 



ture, being more hke condenfed cellular fublfance. It clofe- amined more clearly, are feen to be made up of the ramifica- 



ly inverts each lung, and appears to be fioculer.t on fome tions of the great blood-vcffels, the broiichiac, and very 



parts of its furface, and to adliere to the parietes of the minute air-cells. 



cheft. The other coat is common to both lungs; it is ex- When the brorchias enter the lungs, their chief brandies, 



tended from each fide of the cheft to the dorfal fpine acrofs inftead of being regularly and equally diftributcd, pafs 



tiie anterior furface of the lungs. It is connefted in a de- directly to ceitain points upon the furface of the lung,<i, 



gree to the fort-part of the fpine, and inclofes at this place and there terminate in feveral foramina, which commiiricate 



the trunk of tlie defcending aorta, fuffering the coeliac ar- with the great air-cell j of the body ; thefe branches alfo of 



tery to pafs through it. It has no intimate union with the the broiicliii retain in their llruclure, almoll throughout 



proper tunic of the lungs except at the openings of the air- their extent, fome cartilaginous rings. The ramilicatiuiLs of 



cells, and armmd the entrance of the great veffcb of the tlie air tube which really fupply the fubllance of the lungs, 



lungs. The texture of this coat appears to be tendinous ; are but branches of thole which go to the cells. They are 



its fibres all run in the tranfverfe direction ; and in large birds comparatively fmall, and entirely coivpcfed of membi-anes. 



they are evidciulv white. This aponturofis is not equally 'I'his ftrufturc accounts for the fltfliy appearance and folid 



ftrong upon every part of the lungs; at the upper part, feel of the iunij.s, and explair.s why birds are able to fill 



and elpeeially above where the vcflels enter, it is fo weak their air-cells witli fo much eale and rapidity. 



as often to be hardly vifible. jllr- Cells. 



In all birds there would appear to be fome mufcular fibres Although phyfiologifts are not agreed with refpeft to the 



pafTing from the fide of the cheft upon the aponeuioiis of ufes which thefe part;- fer^-e in birds, yet as they are ini- 



the lungs. 'I'hefe are very diftiuttly to be feen in the mediately connected with the lurgs, it feems moll proper 



larger fptcies, in fome of which the mufcles of the lungs are to delcribe them in this place. It is one of the mofl re- 



of confiderable ftrength. The anatomilis of the French markable and peculiar tircumftanccs in the anatomy of 



academy obferved fix Itrong flips of mufcle on each fide of birds, that the atmofpheric air has a ready paffage to almoft 



the body in the ojlrkh and cajfowary. They arofe from the every part of the interior of their bodies, 



ribs which come from the fpine, near their }uncliOu with The air-cells, according to their fiiuation, may be divided 



3 F z into 



