LUNGS. 



lion may thus malce tliem fpecifically Rghtei* tlian water ; 

 not to mention, that the child may have breathed and died 

 afterwards : fo that the mere naked circumftauce of the 

 lung fwimming is altogether an infiifficient proof that the 

 child has been murdered ; and to condemn a mother to 

 death on fiich gronnds, exhibits a degree of ignorance and 

 barbarity worthy only of the dark ages. 



The increafe of abfolute bulk in the lungs after birth is a 

 phenomenon very worthy of being remarked. We have 

 ftated already, that thefe organs in the foetus, at full time, 

 are y'{,th of the body. According to the reicarches of fonie 

 German and French anatomifts, they are no more than 

 Tr'jth, or -jVth in a child who has breathed. There may be 

 ibme variation in this point, but the organs are never fo 

 light as to approach at all to the proportion wliich they ex- 

 hibit before birth ; a faft which is highly important in its 

 application to quellions of fuppoied infanticide. 



The colour of the lungs does not remain through life the 

 fame as at the time of birth. In tlie earlier years it has dill 

 the reddifli, mixed with a tint of yellow, which we have al- 

 ready mentioned. After the twentieth year the livid or 

 black fpots appear, and become more uumerous as age ad- 

 vances. 



Phyjlology of the Lungs. — Two very different kinds of 

 phenomena take place in the lungs. The firll are entirely 

 mechanical, and relate to the motions of the fides of the 

 cheft, by which the cavity is enlarged or diminidied ; and to 

 the dilatation or contraftion of the air-cells, and the adniif- 

 fion and expullion of the air, which are confequent on thefe 

 motions. Thefe have been already confidered in thofe parts 

 of the prefent article which relate to the motions of the 

 thorax. The phenomena of the fecond kind are purely 

 chemical, and confiil of the various alterations which the 

 refpired air undergoes, of the changes elFeftcd in the com- 

 polition of the blood, &c. For an account of thefe, the 

 reader is referred to Resi'inATiON, and Heat, /Iniimil. 



Thefe two divifions of the rcfpiratory phenomena belong 

 refpeftivcly to the two great clafl'es of vital proceflcs ; the 

 animal and organic. The motions of the cheft are per- 

 formed by voluntary mulcles, and confequently are fubjeft 

 to the influence of the brain : hence a fetlion of the medulla 

 fpinalis above the origin of the phrenic nerve, or a divilion 

 <H the nerves which fupply the mufcles of refpiration, im- 

 njediately annihilates thefe motions. Commonly, indeed, 

 the motions of the cheft are performed fpontancoufly, that 

 is, without any exertion of the will ; and they go on during 

 fleep, when the aftion of all voluntary organs is fufpcnded. 

 But an aft of the will can accelerate, retard, or otherwife 

 modify the movements of the cheft ; and many of the 

 mufcles coneerncd afTilt in moving the trunk, on occalions 

 that have nothing to do with refpiration. The changes of 

 the blood, on the other hand, go on in the capillaries, and" 

 are performed without our conlcioufnefs : the brain has no 

 influence on ttem. The refpiratory funftions, then, offer 

 the point of union of the animal and organic lives, in which 

 thefe may reciprocally influence each other. 



The chemical and mechanical phenomena of refpiration 

 are in a ftate of mfitual dependence : the interruption of one 

 is always quickly followed by the ceflatioii of the other. 

 Without the former, the latter would have no materials to 

 aft upon. If the mechauical .phenomena were interrupted, 

 the blood would no longer be lit to excite the brain ; and 

 that organ could not influence, in the proper manner, the 

 intercoftal mufcles of the diaphragm : hence thefe mufcles 

 would become inaftive, and even the mechanical phenomena 

 inull ceafe. 



The heart does not influence thefe two kinds of phenomena 

 in the fame way. 



The heart of black blood has obvioufly no power over the 

 mechanical phenomena of the lungs ; but it is ellentially con- 

 cerned in producing the chemical phenomena, as it fends to 

 the organ the fluid v.'hich derives certain properties fron; the 

 air, and imparts others to it. Thus, when the funftions of 

 the auricle or ventricle uf blaek blood, or of the great 

 venous trunks, are interrupted, as by a wound, or a liga- 

 ture applied in experiments, the chemical phenomena are at 

 once annihilated ; but the dilatation and contraftion of the 

 cheft ilill goes on. No blood arrives at the left ventricle, 

 and confequently the requifite motion cannot be imparted to 

 the brai:i : hence its funftions are iufpended, and confe- 

 quently the intercoftal mufcles and diaphragm ceafe to ^ 

 aft. 



In the cafe of a wound afFefting the auricle or ventricle 

 of red blood, the aorta, or its great branches, when a liga- 

 ture is artilicially apphed to the latter, or an anenrifm 

 burfts, &c. the funttions of the lungs ceafe in the following 

 order: i. No more impnlfe communicated to the brain; 

 2. No more motion of that organ ; 3. No more aftion ex- 

 erted on the mufcles, and confequently no more contraftion 

 of tlie intercoftals ar.d diaphragm ; 4. No more mechanical 

 phenomena. Without the latter, the chemical phenomena 

 cinnot take place : \n the foregoing cafe, they were Itopped 

 for want of blood ; in this, they ceafe from the interruption 

 in the fupply of air. 



The preceding obfervations are derived from the Re- 

 cherches Phyfiologiques of Bichiit. In the 6tli, 7th, 8th, 

 and 9th articles of the fecond part of that work, he has en- 

 tered at length into the confideration of the influence of the 

 lungs on the heart, the brain, and the organs of tlie body in 

 general ; of which fubjefts he has given more clear and cou- 

 nefted views than any other phyfiologift. We fliall, there- 

 fore, avail ourfelves of his labours in this concluding divifion 

 of the prefent article. 



Influence of the Death of the Lung upon that of the Heart. -~ 

 The ceflation of aftion in the lungs m^ begin either in the 

 mechanical or the chemical phenomena. A wound expofing 

 them extenfively on both fides of the chelt, and producing 

 their fudden coUapfe ; a divifion of the fpinal marrow fud- 

 dcnly paralyfing the intercoftal mufcles and diaphragm ; are 

 cafes in which the death of the lungs begins in the me- 

 chanical phenomena. It commences in the chemical, in 

 afphyxia from noxious gafes, from ftrangulation, fubmerfion, 

 expofure in vacuo, &c. 



The heart's action can be interrupted by the cefTation of 

 the mechanical phenomena of the lungs only in two ways : 

 I. Direftly, if the blood meets in the lungs with a real me- 

 chanical obftacle to its circulation ; 2. Indireftly, becaufe 

 where the mechar.ical aftion of the lungs ceafes, they no 

 longer receive air, which is neceflary to their chemical phe- 

 nomena, the cefl'ation of which interrupts the aftion of the 

 heart. 



All phyiiologifts have admitted that the pulmonary cir. 

 dilation is interrupted in the former of thefe two ways. 

 They have conceived, that where the lung is not diftended, 

 its veflels are folded and comprefl'ed, and therefore tranfmit 

 the blood with difficulty : and by this explanation, derived 

 from hydraulic phenomena, they have accounted for the 

 death which enlues, where expiration is too long con- 

 tinued. 



Goodwyn proved that a fufficient quantity of air remained 

 in the pulmonary veficles to allow mechanically the paflTage 

 of the blood; and, confequently, that protrafted expira* 

 tioii is not fatal in the way commonly fuppofed. (Con- 



neftioo 



