LUNGS. 



thorax in the h'ving fuhjcft, the Iting falls from the fides of 

 the cavity, becomes diminiflied in fize, or, in technical lan- 

 guage, collapfes, and remains motionlefs. Such is the repre- 

 lentation given by Haller (Element. Phyfiol. lib. viii. feft. 2. 

 J 6.) If an extenfive wound be made on botli fides, it 

 feems generally admitted that the lungs are rendered mo- 

 tionlefs, that refpiration (lops, and the animal dies. But 

 it is not equally clear that a fmall wound is attended inva- 

 riably with collapfe and a fatal termination. Cafes are 

 recorded, in which penetrating wounds of the cheft have 

 been attended with protrufion of the hmg — a (late apparently 

 the direft reverfe of collapfe. And Mr. Norris, who had 

 met with fuch an inilance, opened the thorax in (lieep, on 

 oae and both lldes, fufficiently to enable him to introduce 

 a finger. Refpiration was not rendered difRcult. (Sec 

 Memoirs of the Med. Soc. of London, vol. iii.) Tims it 

 (hould feem that the fize of the wound influences tlje refult of 

 the experiment in a living aaimal ; which is not irrcconcile- 

 able to the reprefentation we have already given of the palTive 

 ftate of the lung. For the furface expofed to the external 

 prelfure of the atmofphere by a fmall wound may not conn- 

 teraft the effeft produced by the contaft of the two plcurs 

 in the whole of the reft of their extent. In all thefe experi- 

 ments the wound (hould be carefully kept open, if we are 

 to derive any inilruclive inferences from the refult : if its 

 fides are allowed to come in contaft, no collapfe of the 

 lung could be expedled. We do not know how to explain 

 the protrufion of the lung from wounds. 



If a wound be made in the lung, when there is no commu- 

 nication between the thorax and the external air, as by a 

 broken rib, air efcapes into the thorax, and cannot pafs out : 

 a collapfe of the lung is a necelfary confequence. This is 

 what occurs in emphyfema, and occafions the difiiculty in 

 breathing ; the air alfo efcapes through the wound of the 

 pleura into the cellular fubftance of tlie body. 



When a wound is made into the cheft, in the dead fub- 

 jeft, the lung, which was before in contact with the pleura, 

 immediately recedes from it. The feparation is more marked 

 in front, lefs at the fides ; and at laft the lung, much dimi- 

 nifhed in volume, lies againil the back of the cheft. Of courfe 

 an empty fpace is left, proportioned to the collapfe of the 

 lung, and the pleura is ftretched over this, with a whitidi 

 opaque appearance. This experiment never fails, except 

 when the lung is adherent. The air contained in the cheft 

 at the time of death is cooled as the reft of the body grows 

 cold; its volume muft be diminilhed, and the lung containing 

 it muft undergo a correfponding diminution, by virtue of its 

 contraClility of tifTue. Hence a tendency to the formation 

 of a vacuum enfues, in confequence of which the prefture 

 of the external air puflies the diaphragm ftrongly upwards, 

 and makes it very concave towards the abdomen. This is 

 the condition in which that mufcle is conftantly found in the 

 dead fubjedl, although we might fuppofe that the weight of 

 the thoracic contents, prefTmg on it above perpendicularly, 

 would drive it downwards when it is no longer fupported by 

 the abdominal vifcera below. If a fmall opening be made 

 in it penetrating the cheil, it immediately finks, and a ipace 

 is created above it by the atmofpheric air entering the ca- 

 vity. 



How is the collapfe of the lung In the dead fubjeft to be 

 explained ? Are we to conceive that air efcapes through the 

 glottis when the lung finks in confequence of an opening in 

 the cheft ? On this fuppofition the organ muft previoudy 

 have been maintained by its contadl with the fides of the 

 cavity, in a ftate of greater diftention than it vi'ould exhibit 

 if left to itfelf. The accefs of the air to the thorax enables 

 the Isng to pafs into its natural ftate, by allowing its con- 



Vol. XXI. 



tradiiity of tifTje full fcopefor exertion. But vi-e have af- 

 certained that the phenomenoil, called collapfe of the lungs, 

 takes place in the dead body, wlien a ligature is placed oa 

 the trachea, fo that the contra<flility of tiffue cannot operate. 

 It depends entirely on the finking of the diaphragm, wliich 

 gives way towards the abdomen, and is followed by the lung. 

 The latter organ therefore is not diminidicd in fize, and can- 

 not with any propriety be faid to have fuflcrtd collapfe. 

 Let it be remembered that the concavity of the diaphragm 

 is maintained by the prelTure of the atmofpI;ere, forcing i: 

 into the cheft, to fill the fpace left by the gradual dimi- 

 nution of volume of the lung conlequent oir the cooling of 

 the air, and its contradtility of tifTue ; and that this arifes en- 

 tirely from the accurate mutual contact of the lung and tho- 

 racic cavity. When the latter is expofed, the air prelTes 

 on the lung at tlic fituation of this expofure above, as much 

 as it does againil the diaphragm below, and thtfc two organs 

 confequcntly take that pofiiisn which their weight and con- 

 nedtions, independently of any other caufcs. would deter- 

 iiiine. We believe that the contractility of tilTue of the 

 lung has been exerted nearly to its full extent, before the 

 chf ft is opened, and that it would be exerted to the utmoft 

 extent, if the diaphra;;m could be forced up fuflicien'.ly to 

 fill all the fpace left by the cor.traftion of the organ. It 

 feems to us that the lung does contraS after the cheft has been 

 opened, and confequcntly that the diaphragm is not capable 

 of filling all the fpace which the contractility of the lung 

 might leave. Bichat refers the collapfe of the lung in the 

 dead fubjeft entirely to the coohng of the air contained in thu 

 organ atter death. This, he fays, prodi'res a vacuum 

 between the lung and the pleura coftalis ; lue lung collapfes 

 before the cheft is opened, becaufe the air-cells contract in ■ 

 proportion as the air is condenfed. Tl.c affcrtion that a 

 vacuum exifts is contrary to all obfervation ; indeed the thing 

 is obvioufty inipofiiblc. If we underftand him rightly, he 

 denies that the collapfe takes place on opening the cheft. 

 "Thus," fays he, " there is this difference between opening 

 a dead and a living body : in the former the lung ha? already 

 coUapfed ; in the latter it collapfes at the inftant of the 

 opening. The contraction of the cells, when the cooled air 

 is condenfed and occupies lefs fpace, is an effeft of the ccn- 

 traftility of tiffue, which remains in the organs to a certain 

 degree after death. Moreover, if the lung collapfed in the 

 dead body at the moment of opening the cheft, the caufc 

 would be in the prelTure of the external air, whi.h would ex. 

 pel through the trachea what was contained in the organ. 

 But if, in order to prevent the exit of the air, you clofe the 

 trachea, and then open the cheft, the lung is found in the 

 fame ftate of collapfe ; therefore the air h.ad quitted it al- 

 ready. Make the fame experiment on a living animal, and 

 you will always prevent the collapfe of tW; lung." RJ- 

 cherches fur la Vie ct la Mort, p. 193, note i. 



It remains for us to advert again to the feroi'.s fccrctioo 

 which moiftens the furface of the pleura. Is this feorction 

 neceflfary to the phenomena of refpiration ? is that function 

 fenfibly impeded, when the ferous fluid is no longer pro- 

 duced, and the pleura pulmonalis and coftalis are united to- 

 gether throughout ? For a long time the affirmative of this 

 qucftion has been maintained, and it has even been ufual to 

 attribute habitual difiiculty of breathing to adhefioiis be- 

 tween the lungs and pleur*. Yet the following confidera- 

 tlons render tliis fuppofition very doubtful. I. It has been 

 clearly proved, that in the healthy ftate the lungs and the 

 containing cavities are perfectly contiguous, both in infpira- 

 tion and exfpiration : reafoning alone might have (hewn this. 

 What end do the movemetits of the chelt ferve, if the lung* 

 poffefs in themfelves an independent power of motiop ? 

 4 L * Since^ 



