Thorax (199),, 65. SOME OBSERVATONS ON THE CO-ORDNATON DAPHRAGMATC AND RB MOVEMENT N RESPRATON BY HERBERT HERXHEMER Surgcal Unt, Unversty College Hosptal, London Daphragm and ntercostal muscles together ventlate the lungs. Lttle s known about the proporton n whch they share n ths work. Such knowledge, however, s necessary f we want to understand the aetology of certan respratory dsorders. An attempt has been made, therefore, to nvestgate the part played by daphragm and ntercostal muscles n the exchange of ar. METHOD Tracngs of the respraton were made wth a spromefer of the Benedct-Roth type to whch a flowmeter was attached. Oxygen was suppled contnuously through ths flowmeter at the same rate at whch t dsappeared from the sprometer. The tracngs were thus kept horzontal. After quet breathng had been recorded for some mnutes the subject was asked,to nhale and exhale fully, and the vtal capacty was recorded. Ths was repeated several tmes at ntervals of one mnute or more. At the same tme the rb movements were recorded by means of the thoracograph descrbed by Verzr (195). Ths nstrument permts the accurate tracng of any change n the crcumference of the chest at any gven level.* t s therefore possble to state how much the chest expands or contracts durng a sngle tdal breath, or durng a full nspraton or expraton. The tracng thus appears very smlar to a sprometrc tracng, showng the level at whch the tdal ar exchange occurs between the lmts of nspraton and expraton (Plate a). But unlke the sprometrc tracng t does not represent a volume of ar moved but the changes n the crcumference of the chest at a certan level. f the tdal ar level moves up or down t means that normal quet breathng s carred out by a more or less nflated chest. As a rule the nstrument was appled at the level of the thrd to fourth rbs. The apparatus conssts of a flat steel band whch s put round the chest. ts ends are hooked on to a recordng machne whch rests on the chest. Each expanson of the chest pulls at the recordng pencl, whch records ts movements on rotatng wax paper. Contracton of the chest permts a sprng to pull the pencl back towards ts prevous poston. The advantage of ths apparatus compared wth the stethograph s that ts recordngs are n drect proporton to the actual changes n chest crcumference. OF The smultaneous use of both tracngs serves the purpose of studyng separately the extent of the daphragmatc and rb movements. The volume of the total ar exchange, as gven by the sprometer tracng, depends on both daphragmatc and costal movement. f, at the same tme, costal movement s recorded separately, the comparson of the tracngs wll permt a concluson as to the contrbuton of the costal movement to the volume of ar exchange. f ther excursons reman n the same proporton the shares taken by daphragm and rbs have remaned constant. f the daphragm takes no part n the ventlaton, the rb movement can be expected to ncrease to ts maxmum. Ths form of pure costal breathng s sometmes seen durng the asthmatc attack. f the daphragm only s actve, no rb movement wll be seen on the tracng. Ths can be notced frequently n normal subjects durng quet breathng. n many cases, and n almost all n whom breathng exceeds the basal requrements, the share of rbs and daphragm changes rapdly and contnuously, as may be expected of a functon controlled by so many factors. The range of rb movement to be expected can be seen from the followng mathematcal consderaton: f the thorax s regarded as a cylnder wth a radus of 50 and a heght of 20 cm., ts crcumference would be c = 100 cm. For an ncrease of c from 100 cm. to 102 cm. the volume of the cylnder would ncrease by 636 c.cm. Therefore, for 100 c.cm.. change of volume the change of the crcumference would be 6.36 3.2 mm. Ths calculaton s, of course, only approxmately vald for the thorax, as ts shape s rregular. Were t to hold for pure costal movement, we should, n practce, not observe hgher values than 3.2 mm. per 100 c.cm. ventlaton. n fact, such hgh values are rare n normal subjects. Only n four experments out of 70, values between 3.0 and 3.6 were observed, the latter occurrng only once. A number of asthmatc patents, however, showed values of just under.0 mm. durng an attack, at a tme when the daphragm was n a low poston, and when no movement could be seen radologcally whch could be clearly dentfed as nspratory or expratory.
66 t s therefore assumed that almost pure rb movemnent s present f the movement of 100 c.cm. of ar requres 3.5 to.0 mm. change n chest crcumference, and that pure daphragmatc movement s present when no rb movement can be recorded. As these extremes are the excepton, and the smultaneous acton of daphragm and rbs the rule, at least n normal subjects, t s mpossble to -assess ther absolute shares by our method of smultaneous recordng. t s, however, possble to observe changes n the proporton of ther share under varous condtons-for nstance, n the producton of the complemental and the reserve ar, n the nspratory and expratory movement, and n changes of body poston. The use of ths method s lmted by the fact that t does not gve absolute values. Another lmtnfg factor s that the movement of the upper rbs does not necessarly represent a'so the movement of the lower rbs. For ths reason we have n some cases measured the chest crcumference also at the level of the eghth to nnth rbs. A further possble source of error s that the rbs move more ar per mm. chest expanson as the chest becomes wder. f one regards the chest crcumference as the crcumference of a cylnder wth the radus r, the volume of ths cylnder wll be 7Tr2h. An ncrease of r by, say, 1 mm. wll cause the cylnder volume to ncrease more when r s large than when r s small. f ths s appled to the chest t means that the ncrease of crcumference by 1 mm. of an nflated chest wll produce a greater ncrease of volume than the same crcumference ncrease of a deflated chest. However, the dfference can be shown to be small. f the chest crcumference n full expraton be 100 cm. and ncreases by 1 mm., ts volume wll ncrease by 31.8 c.cm. f ts heght s 20 cm. f the same happens n full nspraton at 110 cm. crcumference, the volume ncrease wll be 38.2 c.cm. The dfference of 6. c.cm. between these two extremes wll not be of mportance for our observatons. A convenent way of determnng the relatve actvty of rbs and daphragm durng ventlaton s to express the costal movement n mm. per 100 c.cm. of ar exchanged. As has been shown, the maxmum of ths fgure wll le near mm.; t represents almost pure costal movement, whlst ts mnmurm, durng pure daphragmatc movement, wll be zero. The hgher the fgure, the more rb movement s nvolved. A fgure below 0.5 mm. wll mean that very lttle costal movement and manly daphragmatc movement has taken place, whereas a fgure above 3.0 mm. ndcates lttle daphragmatc actvty wth prevalent costal movement. Ths method has been used for the nvestgaton of the subdvsons of the vtal capacty n varous postons of the body. The modfcatons used for other condtons wll be descrbed under the approprate headngs. COMPLEMENTAL AND RESERVE AR Fourteen (eght female, sx male) healthy subjects between 15 and 25 years of age were traned HERBERT HERXEMER tll ther breathng was farly regular and they could be reled upon to produce the same vtal capacty wthn a range of 150 c.cm. at any tme. STANDNG PosToN.-The results are shown n the Table, and a representatve example s gven n Plate a. The two graphs have been adapted photographcally so that both are read from left to rght and cover the same dstance for the same tme nterval. t can be seen that both tracngs are smlar: the tdal ar s easly dentfed n both, and the measurement of the maxmum nspraton from the upper lmt of the tdal ar (we have excluded the tdal ar from the complemental ar) and of the maxmum expraton from the lower end of the tdal ar (reserve ar) s a very smple procedure. The Table shows, n spte of great ndvdual varaton, some remarkable unformty for the standng poston: the complemental ar (the upper fgure) les, wth one excepton, above 2 and several tmes above 3 mm.; whlst the lower fgure, representng the reserve ar, n all cases but one s below 1.0 and often below 0.5 mm. Ths. means that n almost all cases the ventlaton has been carred out by both rbs and daphragm, but that the rbs had very lttle or practcally no share n the movement of the reserve ar. The share of the rbs n the movement of the complemental ar, however, s consderable. The observaton that the reserve ar s moved manly by the daphragm ncreases the dagnostc mportance of the reserve ar. We know that n emphysema the daphragm s kept at a low level, and that t cannot be lowered very much more on maxmum nspraton. We would therefore expect the complemental ar n emphysema to be small, as t would be moved manly by the rbs, wth lttle support from the daphragm. On the other hand, the reserve ar should be enlarged because from ts lower level the daphragm (f t s fully moble) can be moved upwards over a greater dstance than from a medum level n a normal person. Both expectatons are confrmed by actual observaton. n emphysema the reserve ar s often ncreased and the complemental ar correspondngly small. There are a number of people n whom ths s not so. n these the daphragm s not fully moble, ether because of the opposng bronchal spasm or for other reasons. Under such condtons the vtal capacty s consderably reduced, and n those patents wth moderate emphysema n whom t s normal or lttle reduced the reserve ar percentage s, n my experence, always abnormally large. Other observers. have had smlar results. Hurtado and others (193)
Upperr rbs Lower rbs Lo. Jo.. X Ha. Ja... Po... (Ma... Mo. Lo... tpa.. - (Ma.... DAPHRAGM AND RB MOVEMENT N RESPRATON TABLE CHANGE OF CHE CRCUMFERNCE N MM. FOR 100 C.CM. OF AM EXCHANGD (Upper fgure: complemental ar; lower fgure: reserve ar) Female subjects Male subjects Name Standng Sttng Supne Name Standng Sttng Supne. 2.3 0.35 2.3 0.73 3.57 0.3 3.12 0.76 2.0 0.38 2. 0.78 3.12 0.89 3.70 0.38 2.28 0.19 1.92 0.20 2.3 0.50 3.12 0.90 2.00 1.18 1.66 0.97 ha've seen an average reserve ar of 29.2 per cent of the vtal capacty n 26 cases of 'emphysema, whlst ther normal cases n the same poston (supne) show an average between 17 and 23 per cent of the vtal capacty (Hurtado and others, 193; Kaltreder and others, 1938). Jmenez Daz and others (192) also found the reserve ar ncreased. Another practcal applcaton of our observatons concerns subjects n whom the reserve ar s small. Ths occurs n obese persons who have a large amount of fat n the'abdomen and n whom the daphragm s found at an abnormally hgh level.. n these persons a small reserve ar can be expected, as the daphragm cannot rse as could from 1.35 1.0 3.57 2.00 1.75 1.16 1.82 0.9 1.75 1.72 1.82 1.59 2.22 2.18 1.85 1.92 1.33 0.50 much from a hgh level poston as t a normal md-poston. Observaton shows that most obese persons have ndeed an abnormally small reserve ar. Sa.~~~~~~~~~~~~~~~~~~~~ Sa. 2. 0.71 Ga. El. Se. Me. He. Sa. He. 2.3 0.62 2.39 0.59 2.77 1.1 2.18 0.0 1.9 0.55 2.86 0.26 2.0 0.63 2.0 0.72 2.39 1.1 1.82 1.32 1.82 1.33 1.92 1.59 1.33 0.93 0.90 0.90 1.72 1.59 1.31 1.15 Another such correlaton of daphragmatc acton and reserve ar s found n' the 'transton from the standng to the supne poston. As Hofbauer (1921), Lvngstone (1928), and Herxhemer (198) have shown, the level of the daphragn shfts upwards when the poston of the patent changes from standng or sttng to lyng. Kaltreder and others (1938) have shown that at the same tme the reserve ar decreases sharply (from 30 per cent n the sttng poston to 18 per cent n the lyng poston). have found a smlar dfference n the transton from standng to lyng (from 37 per cent to 2 per cent). The tdal ar n the standng poston s often exchanged wthout any notceable partcpaton of rb movement. There are, however, great ndvdual varatons. n many subjects rb movement s absent, or almost absent, when they are standng 67
68 n a relaxed atttude-for nstance, leanng aganst a wall. Breathng s, under these crcumstances, exclusvely daphragmatc. But the slghtest muscular exerton or, n some persons, exctement brngs the rbs nto acton at once, and ths wll contnue for some mnutes after cessaton of the cause. The lower part of the Table shows the values found when the thoracograph was appled to the lower nstead of the upper rbs. The absolute fgures, as one would expect, are dfferent from those for the upper rbs, but the essental dfference between the complemental ar and the reserve ar remans the same: the share of the daphragm n the movement of the reserve ar s very much greater than n the movement of the complementary ar; n three out of the four subjects the rbs have hardly any share. SUPNE AND STTNG POSTONS.-There s a defnte dfference between the results n the supne and n the standng postons, as shown n the Table. The complemental ar (upper fgures) stll shows hgher values than the reserve ar (lower fgures). Ths ndcates that n the complemental ar move- -ment the daphragm has a smaller share than n the reserve ar; but the dfference between them s not as pronounced as n the standng poston, and n a few subjects the shares are even dentcal for both subdvsons. On the whole, the share of the rbs n the complemental ar s not as marked as before, although prevalent, and the share of the daphragm n the reserve ar s not as predomnant and almost exclusve as n standng. n order to understand ths, we must remember that, durng transton to the lyng poston, the daphragm s shfted upwards. Ths results n a decrease of vtal capacty, and especally of the reserve ar. At the same tme the chest, n most persons, becomes a lttle wder, to compensate partly for the loss of volume caused by the ascendng daphragm. The rbs have to work now n a more outward poston than before and seem more restrcted n ther extreme nspratory movement. The daphragm, on the other hand, s restrcted n ts extreme expratory movement by ts orgnal hgh level. t can now, from ts hgher level, breathe n deeply " more easly " than t can breathe out. Hence ts smaller share n reserve ar and bgger share n complemental ar. The change s reflected also n the tracngs of the tdal ar. Whlst n many persons durng standng the tdal ar s exchanged wthout rb partcpaton, the rbs become actve n the lyng poston. Ths can be seen, for nstance, n Plate a, whch s representatve for the majorty of subjects examned. There s Very lttle costal movement HERBERT HERXHEMER n the standng, and a pronounced ncrease n the lyng, poston. A few nvestgatons have also been made n the sttng poston, and the values obtaned are ncluded n the Table. As mght have been expected, most of the-fgures le between those obtaned n the standng and the lyng postons. NSPRATON AND EXPRATON Orgnally t was taken for granted that nspratory and expratory movements were strctly recprocal: f, for nstance, a complemental ar of 1,500 c.cm. was nspred by costal and daphragmatc movement n a certan proporton, t was assumed that the reverse expratory movement would be carred out n the same proporton. Some observatons, however, threw doubt on ths assumpton. t was seen, for nstance, that after a maxmum nspraton the chest crcumference dd not return to ts former value but remaned greater than before, although exactly the same amount of ar had been exhaled as had been nhaled. Ths ndcated that the daphragm must have assumed a hgher level than before. An example of ths can be seen n Plate lb (pont E). Ths and smlar observatons made t desrable to nvestgate whether sngle fractons of the complemental and of the reserve ar were moved by constant proportons of daphragmatc and costal actons. For ths purpose the subject was,placed so that he could watch the recordng drum of the spromneter. After some quet breathng he was asked to begn a maxmum nspraton but to hold hs breath for about fve seconds at a certan pont, ndcated to hm on the sprometer tracng, usually mdway between tdal ar and nspratory lmt or nearer to the latter. Then he contnued the nspraton to ts lmt and exhaled mmedately, but stopped durng expraton at exactly the same pont where he had nterrupted hs nspraton. After a further fve seconds he contnued the expraton and breathed quetly for some whle. Then the procedure was repeated wth a dfferent pont of nterrupton. Maxmum expratonreserve ar-was treated lkewse. The holdng of the breath was just long enough to cause an nterrupton n both sprometrc and chest tracngs at correspondng ponts. f the tracngs are synchronzed, as n Plate, t s a smple matter to compare dfferent portons of the complemental and reserve ar and the part that rbs and daphragm have played n ther movement. t s surprsng to see that nspraton and expraton are not carred out n the same manner. n the experment reproduced n Plate la, for
(a) Complemental ar PLATE.-(a) Upper part: thoracometer tracng; lower part: sprometer tracng. Note: (1) Costal movement durng quet breathng s almost absent n the Tdal ar standng (at B). (2) (at The A), tdal but present ar level n of the the supne chest poston crcumference has rsen on transton from the standng Reservelar to the supne poston (at C); the chest s now wder than before. (b) Left porton: thoracogram of a subject changng from the standng poston to the supne poston on the tltng table. n each poston one maxmum nspraton s taken. (st- standng, ly = supne.) t can be seen that n the supne poston the chest crcumference s greater than n the standng poston, both n quet breathng and n maxmum nspraton. Rght porton: thoracogram of the same subject n the standng poston. Durng the perods marked P Complemental pressure has been exerted on the abdomnal wall. One maxmum nspraton s carred out wthout ar pressure and one under pressure. t can be seen that under pressure the chest crcumference s greater than wthout, both n quet breathng and n Tdal ar maxmum nspraton. Reserve ar c.cm. Tltng table Standng _r-~ ~ h.~ ~ N
... ',.':"... f, t '-K *.W.,. e; 0 t s a t St S, t. t 0-..w "V-, fn n v S.,1!' 8 ** txa-v, }s+bx }9 st;s. * *F af st z *, X.e {.:..,. ::0 ::8. :: d,,;>d :. j s"....... + lf j! + e XXX' L * '.em*us.-v: '; ', A. PLATE.-(a) Upper part: thoracometer tracng; lower part: sprometer tracng. At ponts A and B the breath was held at about 2,200 c.cm. below the nspratory lmt, and at ponts A' and B' at about 750 c.cm. below t. At ponts C and D the breath was held about 00 c.cm. above the expratory lmt. (b) Upper part: thoracometer tracng; lower part: sprometer tracng. Showng at E falure to return to former level on expraton, so that the daphragm must be assumed at a hgher level than before. At A and B the breath was held 700 c.cm. and at A' and B' 1,300 c.cm. below the nspratory lmt. - ", j 0 Ar j 9. t '8 - U, 7 j 1. 'll..."-..---..-- B : 1 A; A 0. ~~~~~~...9?2 'A.1 B'.1s. kb' qc 1. ;
DAPHRAGM AND RB MOVEMENT N RESPRATON nstance, the subject held hs breath at the same chest volume durng nspraton as durng expraton. At ponts A and B t s held at about 2,200 c.cm. below the nspratory lmt, and at ponts A' and B' t s held at about 750 c.cm. below t, as seen on the sprometrc tracng. f the chest tracng s compared wth t, these ponts le far apart. n both cases the nspraton has been carred out wth a smlar share of rbs and daphragm before and after the nterrupton, the rates for the costal movement varyng not more than from 1.30 to 1.68 mm. for 100 c.cm. of ar. Expraton s qute dfferent. The top parts (above B and B') are done manly by the daphragm, and only n the lower parts do the rbs begn to act. The fgures for the chest movement durng expraton are 0.83 and 0.0 mm. for 100 c.cm. of ar for the top part, and.0 and 1.96 mm. for the lower part..0 mm. ndcates an almost pure costal movement. Ths experment, therefore, shows the followng: nspraton s carred out by the combned acton of both rbs and daphragm durng the whole movement, although they do not act n constant proporton all the tme. The expraton starts wth a lftng of the daphragm whlst the rbs are held at ther nspratory lmt; later, the daphragm moves much less, and n the frst example (AB) s kept stll, whlst the rbs come out of ther nspratory poston and complete the expraton alone. The example n Plate lb shows a very smlar pcture. For the 700 c.cm. of ar on top of ponts A and B the rbs have moved 0.63 mm. per 100 c.cm. n nspraton and 0.1 mm.-hardly at alln expraton. The fgures for ponts A' and B' are 0.77 and 0.27 mnm. for nspraton and expraton. Smlar experments wth the reserve ar gve correspondng results. The frst movement, n ths case expratory, has been nterrupted about mdway (at C), and the shares of rbs and daphragm are about the same before and after the break (near 2.0 mm.). The nspraton, however, starts wth a purely daphragmatc acton, and no rb movement s recorded for these 350 c.cm. The part after the nterrupton s carred out by both, but predomnantly by the rbs (3.1 mm.). Fve dfferent subjects were nvestgated n the same way, and although there are consderable varatons smlar proportons as shown n Plate were found. n most cases the second respratory movement (expratory for the complemental, nspratory for reserve ar) was carred out wth lttle or no movement of the rbs at frst, near the nspratory and expratory lmts, the daphragm dong most of the work. Later, when nearng the md-poston, the rbs take a greater or even predomnant part of the work. There are exceptons to ths rule. Another frequent but less regular occurrence s the tendency of the daphragmatc acton to predomnate n both respratory phases near the nspratory and expratory lmts, though more n the second. Staeheln and Schutze (1912) have found by recordng costal and abdomnal movement stethographcally that durng quet breathng the daphragm s slghtly more actve n the end-postons. Our observatons le n the same drecton. They show that daphragm and costal muscles do not work together n a constant proporton. The proporton vares wdely n dfferent subjects, and t changes rapdly n the same subject durng dfferent stages. There s a contnuous nterchange between rb muscles and daphragm, the co-ordnaton of whch must requre a very ntrcate nervous mechansm. An astonshng feature s that the volume of ar n the chest at md-poston remans the same, as seen from the constant tdal ar level on the sprometer tracng. f the rbs assume another " tdal ar level " (Plate lb, pont E) the daphragm compensates for t by assumng a hgher or lower level. n some subjects ths componsatng mechansm does not functon as well as n others. Our observatons are supported to a certan extent by screenng. f a subject carres out deep nspratons and expratons slowly, t can be seen that at tmes the daphragm hardly moves, although the respraton s contnung at an even rate. Ths phenomenon was frst reported by Hofbauer (1921). t ndcates that rbs and daphragm predomnate alternately n ventlaton. THE EFFECT OF ABDOMNAL PRESSURE t s known that pressure on the abdomnal wall dsplaces the daphragm upwards (Herxhemer, 198). t was found that at the same tme, n spte of ths obstacle to the daphragmatc movement, the vtal capacty decreased only very lttle. We have recorded the effect of abdomnal pressure on the crcumference of the chest. Plate lb (rght part) shows a thoracometer tracng made whle the subject was standng, leanng comfortably aganst a wall. n ths poston a maxmum nspraton and correspondng expraton to tdal ar level was taken. Then manual pressure was appled to the abdomen (ths part of the tracng s marked P). t can be seen that the tdal ar level moves upwards at once. Ths ncrease of the chest crcumference s 1 to 18 mm. f now another maxmum nspraton s taken, the chest becomes wder than t was at the heght of nspraton wthout abdomnal pressure. 71
72 HERBERT HERXHEMER The wdenng of the chest compensates for the loss of chest volume caused by the hgher level of the daphragm. t happens durng quet breathng n most subjects and may reach 20 mm. The ncreased expanson durng maxmum nspraton s not observed so regularly. t seems to depend on the ndvdual ablty of lftng the rbs nto a hgher and more outward poston. The same ncrease n chest crcumference can be obtaned f the subject holds hs breath n maxmum nspraton and pressure s appled to the abdomen: the chest becomes wder under ths pressure and resumes ts former shape when the pressure s released. n many cases the external pressure on the abdomen can be replaced by the weght of the abdomnal vscera pressng aganst the daphragm n the supne poston. The left part of Plate lb shows an experment wth the same subject on the tltng table. When the subject s tlted nto the supne poston, the chest crcumference durng quet breathng ncreases. f now a maxmum nspraton s taken, the crcumference becomes greater than t was when ths was done n the standng poston. t can also be seen that the costal movement durng quet breathng s greater when the daphragm s at a hgher level and the chest s therefore wder. Ths recalls a common observaton: after a heavy meal many people appear to breathe heavly, and ths s releved by loosenng the belt. n ths case the external pressure of the belt has forced up the daphragm and caused the chest to wden. At the same tme t nduces stronger costal movements and a feelng of breathlessness, whch s quckly releved when the belt s loosened and the former type of respraton-daphragmatc breathng-s resumed. CONCLUSONS AND SUMMARY 1. The changes of the chest crcumference have been recorded smultaneously wth the ar volume exchanged. Ths permts an estmaton of the share that the daphragm and the costal muscles have n varous phases of respraton. 2. n the standng poston quet breathng s often purely daphragmatc, whlst n the supne poston the costal muscles take a greater part n t. 3. The complemental ar s moved by both daphragm and costal muscles, but predomnantly by the latter. The reserve ar s moved predomnantly by the daphragm, and n the standng poston often almost exclusvely. n the supne poston the dfferences mentoned are less pronounced and there s a tendency towards an even share.. The drect relatonshp of daphragmatc movement and reserve ar ncreases the dagnostc mportance of the latter. An ncreased reserve ar ndcates a low level daphragm of good moblty. A decreased reserve ar ndcates ether a reduced moblty or a hgh level of the daphragm. A consstently ncreased reserve ar s of dagnostc sgnfcance n emphysema. 5. The proporton of costal and daphragmatc movement changes throughout the respratory cycle. After the nspratory or expratory lmt has been reached by the concerted acton of both, the daphragm starts the reverse movement, whle the rbs are kept n poston or move only lttle; later they jon n, and near md-poston take over most of the acton. 6. Lftng of the daphragm, ether by pressure on the abdomen n the standng poston or by the pressure of the abdomnal vscera n the supne poston, causes an ncrease of the chest crcumference durng quet breathng. On maxmum nspraton the rbs can be lfted more under such pressure than wthout t. Ths accounts for the small reducton n vtal capacty n spte of the consderably hgher level of the daphragm. REFERENCES Daz, C. J., Agesa, A., and Alemany, M. (192). Rev. Cln. Espan., 5, 21; 5, 13. Herxhemer, H. (198). Thorax, 3, 122. Hofbauer, L. (1921). "Atmungspathologe und Therape." Berln and Venna. Hurtado, A., Fray, W. W., Kaltreder, N. L., and Brooks, W. D. (193). J. cln. nvest., 13, 169. Hurtado, A., Kaltreder, N. L., Fray, W. W., Brooks, W. D., and McCann, W. S. (193). J. cln. nvest., 13, 1027. Kaltreder, N. L., Fray, W. W., and Hyde, H. V. Z. (1938). Amer. Rev. Tuberc., 37, 662. Lvngstone, J. L. (1928). Lancet, 1, 75. Verzar, F. (195). "H6henklmaforschungen des Basler Physologschen nsttuts." p. 77. Basle: Benno Schwabe. Staeheln, R., and Schutze, A. (1912). Z. kln. Med., 75, 15.