LUNGS. 



beinGT converted into the red flate, and that this black blood 

 is circiilT.ed thr.rigrh the body by the dill fiirvivinjT aftion 

 of the li"art, Bichat proceeds to (liew that the black blood is 

 not rj s.Hle of maiiitainincr the vital powers and ai'^ivity of 

 the or^rans, which are therefore killed by its contaft. i^he 

 re.l 'lood, he fays, gives to the organs their natural and 

 healthy excitation, by which their vifal powers are fupport- 

 ed. P^nibly this effect mdy be produced by the combina- 

 tion of the differeftt principles that colour it, with the va- 

 rious organs in which it is contained. 



The organs of the animal and of the organic life have 

 their aftiois terminated in different ways. The former, be- 

 ing entiely dependent on the brain, have their funAions fuf- 

 peiided as foon as thofe of the Urain ceafe. We have already 

 (hewn that the contaft of black blood produces the latter ef- 

 feft almoft inftantlv ; confequently the organs of fenfation, 

 locomotion, and the v»,ice, mul be fuddenly paralyfed in 

 afphyxia. But the circulation of the black blood produces 

 ftill further effefts : when it penetrates the nerves, it ren- 

 ders them incapable of keeping up the communication be- 

 tween the brain and the fenfes on one fide, and the locomo- 

 tive and vocal organs on the other. The contact of the 

 black blood with the organs themfelves alfo annihilates their 

 action. Injeft into the crural artery of an animal blood 

 drawn from one of its veins ; the motions are foon weakened 

 very perceptibly, and fometimes a momentary paralyfis is 

 produced. The effeft cannot be afcribed to tying the artery, 

 for that alone is often attended with no fuch confequence, 

 whereas the refult of injecting black blood is always the 

 fame, except indeed that it varies in duration and intenfity. 

 Senfation is alfo manifelHy fufpended in this e.x.periment, but 

 later than the power of motion. The cffeft is always pro- 

 duced, particularly if the injeftion of black blood be re- 

 peated three or four times at fmall intervals. 



The organs of the internal life being independent of the 

 cerebral aftion, have not their functions arrefted, like thofe 

 of the external life, by the fufpenfion of that aftion. It is 

 the contaft of the black blood only that afts in this cafe, 

 and confequently the death of thefe organs has one caiife 

 lefs than that of the locomotive and vocal parts, &c. We 

 have already explained the influence of the black blood on 

 the organs of circulation, and have fhewn how the heart 

 ceafes to aft as foon as it is thoroughly penetrated by that 

 fluid. Its circulation in the veffels of the coats of the arte- 

 ries and veins weakens thofe tubes, and fufpends their aftion. 

 It mud be exceedingly difficult, if not impoflible, to bring 

 forward any ilrift proof that the fecretions, exhalation, and 

 nutrition cannot derive from the black blood materials fuited 

 to their offices ; for that blood does not circulate in the ar- 

 teries long enough to admit of our making experiments on 

 thofe-funftions. We mull rely, therefore, chiefly on the ana- 

 logy of what happens in other parts, to prove that the or- 

 gans of fecretion, exhalation, and nutrition have their func- 

 tions interrupted when black blood is fcnt to them. This 

 ftatemenl is very much corroborated by the quantity of blood 

 found in the velTels of thofe who have perifhed by afphyxia ; 

 it is fo large as to be very troubleforae in diffefting fuch 

 bodies, which might naturally be expcfted when the ufual 

 outlets of the fecretions, &c. are ilopped. 



From the preceding confiderations Bichat concludes, that 

 when the chemical functions of the lungs are interrupted, all 

 the organs of the body ceafe to aft li.nultaneoufiy, in confe- 

 quence of the contaft of black blood ; that their death coin- 

 cides with that of the heart and brain, although it is not de- 

 rived immediately from that caufe ; that, if it were poffible 

 for thefe two organs to receive red blood, while black was 

 fcnt to the others, the fumiiions of the latter would ceafe, 



while thofe of the former would be continued : in a word, 

 that afphyxia is a general phenomenon, taking place at the 

 fame time in all ♦he organs, and not more decidedly marked 

 in any particular one 



By refuming and comparing what has been faid concerning 

 the influence of the lungs on the heart, the brain, and the 

 organs in general, we (hall eafily form an idea how all the 

 funftions fucceffively terminate, when the refpiratory pheno- 

 mena are interrupted. When the mechanical phenomena are 

 fufpended'; i, there are no more chemical phenomena, for want 

 of airto fupportthem; 2, no more aftion of the brain, for want 

 of red blood to excite it ; 3, ceffation of the animal life, 

 that is, of the fenfaiions, locomotion, and the voice, becaufe 

 the organs are no longer excited by the brain, nor by red 

 blood ; 4, ceffation of the general circulation ; 5, ceffation 

 of the capillary circulation, of fecretion, abforption, and 

 exhalation, in confequence of the organs of thofe funftions 

 being no longer excited by red blood ; 6, no more digef- 

 tion, for want of fecretion and excitation of the digeltive 

 organs, &c. 



When the chemical funftions of the lungs are interrupted, 

 the phenomena of death fucceed in a different order : i, in- 

 terruption of the chemical phenomena ; 2, fufpenfion of the 

 aftion of the brain ; 3, ceffation of the fenfations, and of 

 voluntary motions, confequently of the voice, and the me- 

 chanical phenomena of refpiration ; 4, (loppage of the 

 heart's action, and of the general circulation ; 5, termina- 

 tion of the capillary circulation, of the fecretions, exhalation, 

 abforption, and confequently of digeftion ; 6, annihilation 

 of animal heat, which is the refult of all the funftions, and 

 which does not leave the body until every kind of vital pro- 

 cefs is extinguifhed. In whatever fun&ion death may begin, 

 it alw-ays ends in this. 



There is a very intimate conneftion between the brain and 

 the lungs : as foon as the former ceafes to aft, the funftions 

 of the latter are interrupted. This phenomenon, which is 

 conftantly obferved in warm-blooded animals, can happen 

 only in two ways : i, becaufe the aftion of the brain is 

 direftly neceffary to that of the lung ; or 2, becaufe the lat- 

 ter receives from the former an indireft influence through the 

 intercoftal mufcles and diaphragm, an influence which ceafes 

 as foon as the brain becomes inaftive. 



The lung can influence the brain direftly only through tBe 

 par vagum and the great fympathetic nerve. Irritation pf 

 the former renders' refpiration hurried, but this is an effeft 

 produced by any confiderable pain. Divjfion of one nerve 

 of the eighth pair affects the breathing for a time : but tliis 

 goes off, and the refpiratory funftions are then carried on with 

 their accuftomed regularity. If both nerves are cut, refpi- 

 ration is ftiU more hurried : it does not return to its ordi- 

 nary rate, as in the preceding experiment, but continues la- 

 borious for four or five days, when the animal periflies. 

 Hence we fee that the eighth pair is neceffary to the pulmo- 

 nary funftions, and confequently that the brain has fome in- 

 fluence on thefe funftions : hut the agency is not a very 

 aftive or important one, fince the funftions of the lung are 

 continued for a long time without it, and confequently re- 

 fpiration is not fuddenly (lopped, through its interruption in 

 injuries of the brain. Experiments (hew that the iiitercej)- 

 tion of the influence derived from the great fympathetic is 

 equally inadequate to interrupt the funftions of the lungs. 



Smce the lung is not affefted immediately from the inten- 

 ruptipn of the aftion of the brain, there muH be fome intei:- 

 mcdiate organs, through which tlie former is aftcd on by 

 the latter. Thefe are the mufcles of refpiration Subjeft, 

 by the nerves which they receive, to the immediate influence 

 of the braiuj they become paralytic as foon as the aftion of 



the 



