LUNG S. 



tfie right fiJc. For the Ofganifation of tlii.-fe ve.TclB, fee 

 Hjeart. 



The capi'lary vt-ni-ls of the lung are diilribntctl in infinite 

 'number tliroiigh all parts of the orgsn, of the proper timic 

 of which they coinpofe a rery confiderable {liare. As they 

 have no connexion with the nutrition of the part, and pir- 

 fonn no fecrction, they give pafHif^e only to the bh^oel, and 

 are hence remarkably dillinguifhcil from tlie general capil- 

 lary fyfti-m. Thefo vetfels cover in vail proftifit n the 

 air-cells of the hnigs ; fo that when they are injeftod with 

 coloured fluids after death, the wiiole fiiblf ancc of tiie organ 

 appears dyed of the peculiar colonr. In them the blood is 

 expofed to the air, and converted from the dark or venous 

 into the red or arterial ftate. 



The fiibilance of the lungs, on fnperfici.d examinatiovi, 

 offers a fott fpongy niafs, yielding eafily to prcffure, and 

 reftoring itfelf afterwards to its original ftate in an impcrfedl 

 manner. AVIieii we view it more attentiTely, we obferve on 

 the furfacc fmall whltifli lines circnnifcribing fpaces of dif- 

 ferent figures, as triangular, quadrangular, ^c. Thefeare 

 ■called lobules of the lungs, and vary confidcrably in lize as 

 •well as figure. They are again divided into other fmaller 

 parts. Thcfc lobules are all connecled together by a loofe 

 and foft cellular fubllance, which never contains any fat ; 

 and the fame fubllimce unites the rcfleftcd pleura to the ex- 

 ternal fnrface of the lung. If we tear the fubllance of 

 the organ, and inflate it, the air fills the cells of this cellular 

 texture, and makes it more fenljble : it is alfo in fome cafes 

 rendered more obvious, by being the feat of a watery de- 

 polition, which conflitutes anafarca of the lungs. Its cells 

 have no communication with the air veilcles, unlefs the latter 

 be broken by inflation, as when we fqueeze the air in them 

 forcibly, they crack, and the air cfcapes into the cellular 

 texture, uniting the lobuli. On the other hand, we n.ight 

 inflate the cellular fubllance diltindtly from the air-cells. 



Each lobulas of the lung eonfills of a branch of the air- 

 tube with a correfponding proportion of cells, a branch of 

 the pulmonary artery and vein, a portion of the pulmonary 

 capillaries of the bronchial velfels and nervous ramifications, 

 connefted by the cellular fubllance already defcribed. 



The lymphatics of the lungs arc numerous, and divided 

 into a fuperficial and deep-feated fet : the former conflitute 

 a net-work on the furface of the lung, and communicate alfo 

 with the latter. They pafs through numerous glands, called 

 bronchiali placed on the trunks of the air-tubes and blood- 

 ■veffels, partly within, but chiefly without the fubllance of 

 the lung. Other larger glands are fituated about the divi- 

 fion of the trachea, and the abforbents of the right and left 

 lung communicate in them. Some abforbents of the right 

 lung terminate in the right abforbcnt trunk } the reft, with 

 thofe of the left, end in the thoracic du6l, pafTiiiij through 

 glands on the fpine. 



The brsnchial glands are large in fizc, and numerous in 

 proportion to the lung ; but they vary in both thefe re- 

 fpedls in different fubjefts. Several of the fmalleft are found 

 on the bronchi, within the fubftance of the lung. Their 

 colour is the moft remarkable of their properties : in the 

 adult it is a deep livid or black. Their confillence is rather 

 foft, and a coloured fluid may be exprelfed from them, when 

 cut or divided. Il is now clearly afccrtained that thefe 

 bodies belong to the lymphatic fyfteni. Anatomifts for- 

 Werly conceived that they fccretcd a particular fluid, and 

 poured it into the bronchi. We are quite ignorant ot the 

 caufe of their peculiar black colour. 



The lung, then, is made up of the tiffues juft defcribed, 

 covered on the furfacc by the very thin and tranlpaient 

 pleura pu'monalis, which i; conneAed to the organ by 



cellular fubftanes, and gives it tiie finooth external fufc 

 face. 



Dcvilf/p.inenl of the Lungs. — The foetus has RO refpir.i- 

 tion : from the circumllanccs under which it is placed in the 

 uterus, it mull obviouQy be altogether precluded from ex- 

 crcifing that fuui'tion ; but it begins immediately after 

 birlh: hence the lungs, formed nearly as foon as the prin- 

 cipal organ of circulation, poffefs, at n very early period, a 

 conllderable developcment and well-marked form. Their 

 organifation, too, is ]Krfeft, or at leall they are capable (A 

 executing their functions, before the time at which they na- 

 turally come into adtion : for there are inftanccs of ciiildrcn 

 born long before the end sf the ninth month, as, for in. 

 fiance, at the feventh, or even fooner, who have been pre- 

 ferved alive by great care. In the early periods their colour 

 is rcddifli ; they then affumc a flightly tawny hue, which is 

 continued till the time i.f birth, and is not even changed by 

 refpiration, although tlie adinilfion of air into the organs at 

 that time is followed by the entrance of a larger quantity of 

 blood. 



The lobuli are very diftincl in the fcftus, and cafilv fe- 

 parable : the connecting fubllance appears to be more 

 copious. Although the lungs a-c fmall in a fcctus at full 

 time, compared to thofe of a child who has breathed, we 

 cannot fay, as fome anatomifts reprcfent, that they are ex- 

 tremely diminutive, and confined to the back of the cheft. 

 As tbey are at this time entirely free from air, they poffefs 

 a denlity, which makes them link inllantly in water, when 

 plunged into it either entire or in (licee. They are pene- 

 trated by much lefs blood than after breathing lia* begun, 

 and therefore reduced almoll entirely to their folid and or- 

 ganifcd contents : they form at this time about y^th of the 

 weight of the whole body. 



As the function of refpiration, which commences at the 

 moment of birth, goes on afterwards uninterruptedly, and 

 as the phenomena are as regular and perfecl at this time as 

 in more advanced age, we have no reafon to expeft that the 

 intimate llruilure ot the organ, that is, the arrangement of 

 the different component tifl'ues, will be different at that age 

 from what we know of it in the adult : but the valcular 

 trunks belonging to thefe parts exhibit fome peculiarities, 

 of which the details will be found in the articles He.^kt and 



ClKCUL.ATIOM. 



Breathing begins immediately after birth ; the enlarge- 

 ment of the chcll occallons the lungs to be dillended with 

 air, and confequently to become fpeciiically lighter ; a 

 greater quantity of blood paffes through them, and thus 

 they acquire greater abfolute weight. The incrcafe of vo- 

 lume mull be limited by the capability of enlargement in the 

 cheft ; and this cannot be very coiifiderable immediately on 

 birth. This enlarged lize is not, therefore, fufficiently 

 marked, to be relied on as a proof that refpiration has be- 

 gun. It is a vvell-known fadl, which we have already flatcd, 

 that the lungs of an individual, who has breathed, fwim in 

 water, whether they be immerfed entire or in dices. This 

 is a property remarkably contralled with what takes place 

 under the fame treatment before birth. A criterion has 

 been fought for in this fource, to determine, in doubtful 

 cafes, whether a child has been born dead or alive : and the 

 conlideration is a highly important one, from the influence il 

 may produce on medical opinions, in cafes of fufpcited 

 child-murder. AVe fhall only obferve here, that the coti- 

 vullive attempts to cllablifh refpiration, although not fuc- 

 cefsful, may introduce air enough into the lungs to make 

 them buoyant in water ; that attempts to infla"e them, in 

 order to prefervo the child, er after it has died, may have 

 the f.»me cffeftj ttat the (ijfenjjagemeni of air bj- putrefae- 



tiua 



