LUNG S. 



the right fiJc. For the Ofganifation of tli'.fc yc!TcI», fee 

 Ukvrt. 



Tlie capillary vv-fTels oftlie lang are tiiilribiitnl in infinite 

 numhcr tlirough all parts of the org^in, of t!ie prcipcr tifTue 

 (if which they coinpofe a Tery contiderable {liare. As they 

 h ivo no conncflion with the niitrttioii of the part, and per- 

 forin no fecrct:on, they give paffap^e only to the blood, and 

 are hence remarkably diilinguilhed trotn the general ca[)ii. 

 lary fyKem. Thefe veffels cover in vail proftifnn the 

 ai.-cclls of the lungs ; fo that when they are injeftcd with 

 coloured fluids alter death, the whole fubllancc of the organ 

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

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

 i:ito the red or arterial ftate. 



The fubllance of the lungs, on fuperficial examination, 

 tfTers a foft fpongy mafs, yielding eafily to preffure, and 

 reftoring itfelf afterwards to its original ftate in an impcrfedl 

 m'lnner. When we view it more attentively, we obferve on 

 the furface fmall whitifli lines circunifcribing fpaces of dif- 

 ferent figure*!, as triangular, quadrangular, &c. Thcfearc 

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

 ivell as fiijure. They are again divided into other fmaller 

 parts. Thcfe lobules are all connected together by a loofe 

 and foft cellular lubllance, which never contains any fat ; 

 ;,nd the fame fubllance unites the rcflcfted pleura to the ex- 

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

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

 tc.sture, and makes it more fenfible ; it is alfo in fome cafes 

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

 pofition, which conflitutes anafarca of the lu[igs. Its cells 

 have no communication with the air veficles, unlefs the latter 

 b." broken by inflation, as when we fcjueeze the air in them 

 Krcibly, they crack, and the air efcapes into the cellular 

 t.Kture, uniting the Inbu'i. On the other hand, we n-ight 

 i. ilate the cellular i''ubllance dillindlly from the air-cells. 



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

 tube vith a correfponding proportion of cells, a branch of 

 the pulmonary artery and vein, a portion of the pulir.onary 

 capillaries of the bronchial veflels and nervous ramifications, 

 connefted by the cellular fubllance already defcribed. 



The lymphatics of the lungs are numerous, and divided 

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

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

 with the latter. They pafs through numerous glands, called 

 bronchial; 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 

 ling communicate in them. Some abforbents of the right 

 lung terminate iu the right abforbcnt trunk ; the reft, with 

 thofe of the left, end in the thoracic duft, pafling through 

 glands on the fpine. 



The branchial glands are large in Gzc, and numerous in 

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

 fpefts in diflcrent 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 confillcnce is rather 

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

 cut or divided. Il is now clearly afcertained that thefe 

 bodies belong to the lymphatic fyftem. Anatomifls for- 

 Jnerly conceived that they fecreted a particular fluid, and 

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

 taufc of their peculiar black colour. 



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

 covered on the lurfacc by the very thin and tranfparent 

 pkura pu'monaiis, which i; conneded to the organ by 



cellular fubftant*, and gives it the fmooth external fu*. 

 face. 



De\)fli,pement fjf thi Lungs. — The foetus has so refpira- 

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

 iiteru*, it muft obvioiiOy be altogether precluded from ex- 

 ercifiiig that fuuiJtion ; but it begins immedia:ely after 

 birlh; hence the lungs, formed nearly as funn as the prin- 

 cipal organ of circulation, pofTefs, at a very early penod, a 

 conliderable devclopement and well-marked form. Their 

 organilation, too, is ixrfeft, or at leaJl they arc capable of 

 executing tlieir tunction?, before the time at which they na- 

 turally come into aftion : for there are inltances of children 

 born long before the end <-;f the ninth mouth, as, for in- 

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

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

 is reddifli ; they then atTuinc a (lightly tawny hue, which \i 

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

 refpiration, although the admifFion of air into the organs at 

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

 blood. 



The lobuli are very diftinifl in the foetus, and eafily fe- 

 parable : the conncfting fubllance appears to be more 

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

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

 cannot fay, as fome anatomilts reprefent, that they are ex- 

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

 As they are at this time entirely free from air, ihey polTefs 

 a dcnfity, wiiich makes them link inllantly in water, when 

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

 trated by much lefs blood than after breathing ha< begun, 

 and therefore reduced almoft entirely to their fulid and or- 

 ganifed contents : they form at this lime about y^th of the 

 weight of the whole body. 



Ai the funftion of refpiration, which commences at the 

 moment of birth, goes on afterwards uninterruptedlv, and 

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

 in more advanced age, we have no reafou to expetl that the 

 intimate llrufture of 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 vafcular 

 trunks belonging to thefe parts exhibit fome peculiarities, 

 of which the details will be found in the articles H£.\Rr and 



CiRCUL.ATIO.V. 



Breathing begins immediately after birth ; the enlarge- 

 ment of the chcll occafions the lungs to be dirtcnded with 

 air, and confequcntly to become fpeciiically lighter ; a 

 greater quantity of blood paffes through them, and thus 

 they acquire greater abfolute weight. The increafc of vo- 

 lume mull be limited by the capabihty of enlargement in the 

 chell ; and this cannot be very confiderable immediately on 

 birth. This enlarged lize is not, therefore, fufEcitntly 

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

 gun. It ia a well-known fadl, which we have already ftated, 

 that the lungs of an individual, who has breathed, I'wim in 

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

 is a property remarkably contrafled 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 h.is been born dead or alive : and the 

 coniideration is a highly important one, from the influence it 

 may produce on medical opinions, in cafes of fufpcited 

 child-murder. We fhall only oblerve here, that the con- 

 vulfiie attempts to eftablifh refpiration, although not fuc- 

 cefsful, may introduce air enough into the lungs to make 

 them buoyant in water; that attempts to inflate them, in 

 order to preferve the child, er after it has died, may ha^e 

 the fame cfFeft ; that the dii'cngagcmen; of air by putrefac- 

 tion 



