LUNGS. 



redore the diaplira^m to its former (late, and confeqiieiitly 

 diminilhthe capacity of the cheft. 



The enlarfreinont of the tliorax in the circular direftion is 

 ordinarily effffted by the intercoftiil miifcles, fee Inter- 

 tosTALKs) : and tlie fubftquent contntftion is owing partly 

 to the reftoration of the ribs by the elallic power of their 

 cartilages, and partly totheaftion of the triangularis fterni. 

 But other powers affift occafionally, when the circulation 

 .ind confequentlv the breathing are iuirried ; or when dif- 

 ■afe of the chc-it caufes this function to be performed labo- 

 noufly. Under fuch circumftances, every mufcleis brought 

 into aftion that can alFifl in elevating the fternum or ribs, or 

 in fixing the upper pairs of thefe bones. Hence the fcaleni, 

 fterno-cleido-malloidei, fubclavii, cervicales dofccndentes, 

 levatores coftarum, ferrati niagni, ferrati pollici fuperiorts, 

 l.itiflimi dorii, peftorales majores & minores, and trapi'zii, are 

 all employed. The flioulders are elevated, the neck is 

 itretched, and the head itfelf thrown backwards in the moft 

 violent efforts of difficnlt exfpira"ion. There are alfo auxi- 

 liary powers occafionally employed in exfpiration, but thefe 

 are not fo numerous as thofe concerned m infpiration. The 

 ribs may be depreffed, not only by the tnangularis Iterni, 

 but alfo by the obliqui, refti and tranfverfi alulominis, the 

 quadrali lumborum, longifllmi dorfi, facro-lumbaiis, and fer- 

 rati poftici infericres. 



In the healthy fubjccl the enlargement and contraftion of 

 the cheft conftantly fticceed each other, and are performed in 

 a regular alternate manner. The diaphragm and abdominal 

 mufcles feem to be chiefly employed ; but the intercoftal 

 rnufcles alfo aflift. In the female the latterpowers are more 

 concerned in refpiration than in the male. 



Although both modes of refpiration are obfcrved to con- 

 cur in this fundlion in the natural itate, it may be and often 

 is carried on fey one exclufivcly. When a rib is broken, or the 

 pleura inflamed, motion of the chefl is exceedingly painful, 

 and the diaphragm and abdomnial mufcles carry on the 

 funftions alone. On the contrary, in inflammation of the 

 peritoneum, in the laft periods of pregnancy, in large 

 dropfical accuniulations, the abdominal mufcles and dia- 

 phragm cannot aft, and the intercoilals only are then 

 concerned. 



In ordinary refpiration, enlargement and contraftion of 

 the cheft, or infpiration and exfpiration, are performed in re- 

 gidar alternate fucceffion : but this order is often interrupted, 

 and various modifications of the procefs take place, dillin- 

 guithed by particular names. 



In Jlrdining, the diaphragm and abdominal mufcles aft to- 

 gether ; a deep infpirati-.in is firll made, and the diaphragm 

 defce:'ds confiderably ; the abdominal niufcies then contraft, 

 but do not expe.l air from the cheft, as they are refilled by 

 the former power. The aft of ftraining takes place in all 

 powerful exertions of the body : by it the trunk is fixed, and 

 affords a firm point from which the limbs may be moftadvan- 

 tageoufly moved. The ereftors of the fpine at the fame time 

 extend that part, and firmly maintain it in that pofition, 

 Thus all the power of the mufcles moving the limbs is em- 

 ployed in jumping', dragging, pulliing, moving a weight, 

 &c.; and none is loft in moving the thorax or pelvis towards 

 the limbs, which would be the cafe if thofe parts of the 

 trunk were not previoufly fixed. So long as the effort lafts, 

 it is obvious that refpiration muft be interrupted ; hence it is 

 called, in common lan^^ruage, holding the breath : and when 

 it is too long continued, all the inconveniences arifing from 

 fuch interruption take place. 



The powerful aftion of the diaphragm and abdominal 

 mufcles fubjects the contents of the abdomen to prefTure : it 

 impels them and whatever they may contain towards the cavity 



of the pelvis, and muft alfo comprefs the blood-vcffels and alr» 

 forbents. Hence this effort is employed in expelling the con- 

 tents of the ftomach in vomiting, in evacuating the reftum and 

 urinary bladder, and in parturition ; it is fo effential in all 

 thefe cafes, that the different objcfts juft mentioned could net- 

 be accomplifhed without it. Of the amount of the force 

 exerted we may form fomc cftimate, when we fee the effefts 

 occafionally produced by fuch efforts ; — the contents of the 

 abdomen are protruded and form ruptures, the vifcera are 

 torn, and the tend )ns of the abdominal mufcl.'S lacerated. 



Whether the palfage of bile through its dufts, or of cal- 

 culi through the fame tubes or the ureters be facilitated by 

 ftraining, is a doubtful point. 



In panting there are fliort and frequent infpirations, fuc- 

 cecded by Ihort and quick exfpirations. It is accompanied 

 wiih great anxiety, and is attended with, or caufed by, a 

 more rapid return of bl^od to the lungs ; hence it heats and 

 fatigues. It is produced by violent motion of the body, in 

 wounds of the cheft, in difeafes of the refpiratory organs, 

 and ofen in the Itruggle preceding death. 



A long and deep mfpiration, followed by an exfpiration of 

 the f^ime kind, conllitutcs ajigli. It feems to be an effort at 

 promoting the pafTage of the blood through the lungs ; and 

 has been faid to be employed when the aftion of the heart is 

 languid, when it is oppreffed by the quantity of the blood, 

 or when obftacles exift to its paffage through the lungs. 

 Sit-'hing takes pUce under mental afHiftion or coiii'dcrable 

 buddy fatigue : we generally recover from a ftate of fyncope 

 by a figh, and afthmatic pcrfons frequently figh. 



In ya-wn'mg there is a ftill larger infpiration than in 

 fighi'-.g, performed in a very flow and protrafted manner, 

 and accompanied by a fimilar correfpuuding exfpiration. In 

 both a peculiar found is ufually pruduced. The mouth is 

 opened widely, indeed to the utmoft extent that the arti- 

 culation of the lower jaw will allow. Yawning is often 

 ended by a llgh. That it is produced by bodily fatigue, 

 obfer^ed moft fr quently on the approach of deep and on 

 waking, and takes place alf> when h''ngcr is troublcfome ; 

 alfo that newly born ciiildren yawn in their firft attempts at 

 refpiration, are well known fafts , but we cannot explain 

 how this happens. Soemmerring fays, " that the circulation 

 of the blood tlirough the lungs goes on more flowly Ijefore 

 yawning ; and that we endeavour to obviate by a flrong in- 

 fpiration, which may promote the circulation through the 

 lungs, the fenfe of weight, inconvenience, and fleepmcfs 

 that would arife from this caufe." De Corporis humani Fa- 

 brica, t. vi. p. 82. 



Coughing is an effort of the refpiratory organs, generally ■ 

 made for tlie purpofe of removing from the trachea or its ^ 

 branches fome irritating matter, as mucus, pus, or any 

 foreign body, through the means of powerful exlpiraticns, 

 preceded by fimilar infpirations. Yet the prefence of a 

 ftimuluS in the fituation juft mentioned is not neceffary, 

 ahhough it is the moft frequent caufe : irritation of the dia- 

 phragm, as from difeafed liver, or an aftion of the will, can 

 produce coughing. A lar^;e quantity of air furnilhed by a 

 confider.ible infpiration, is violently and luddenly expelled, 

 with a confiderable noifc, by a very llrong and almoil con- 

 vulfive exfpiration, and in its paliage clears away mucus, or 

 any thing elfe which may happen to be in the air paffages. 

 Tlie air may be driven out at once or at leveral exfpirations: 

 in the latter cafe tie exfpirations are continued often as long 

 as any air can be expelled, and the emptied chelt is again 

 fupplied by an infpiration accompanied with a peculiar 

 noile, as in the hooping cough. Violent a^id protrafted 

 coughing from the interruption of the refpiratory pheno- . 

 xneiia, io accompanied with turgefcer.ee and livid colour of 



the 



