STUDIES IN CENTRE OF GRAVITY CHANGES
No. 3
AN INVESTIGATION OF THK SEX DIFEKRENCK IN RESPIRATION, BY
MEASUREMENT OE THE RESPIRATORY VARIATION IN THE
CENTRK OE GRAVITY.
by
P. S. COTTON
(Prom the Dejiartment of Physiologj-. University of Sydney).
INTRODUCTFON.
Many iiivestlfjatnrs have attempted to decidf wlietlier the relative ]ireponderance of thoracic respiration was an essential or imposed cliarat-feristic
of fhe female sex. Most of the investijiiations were carried out many years a|i:o,
and in the meantime radical ehanf^'es liave taken place in women's clothinj;,
which now restricts abdominal movement less than formerly. The first reference to a sexual differencf in the character of the resi)iration discoverable was
hy Boerhaave in 1744. He concluded from bis observations that the difference was manifested even in tbe case of infants, lioerbaave rcjiariled the
thoracic ty|>e of breathing as a provision of nature against tbe restriction of a
distended uterus to diai)hragmatic movement. All subsequent workers, however, except Ilutchinson, a<rree that the difference is not manifested in children.
Hutchinson (1^'ItJ) concluded tbat a greater tboracic respiration was characteristic of the female sex, and that even in girls of 11 to 24 years of age tbe
respiration could not be counted by observing tbe abdomen. On the other hand.
Mays (1887). who examined 82 Indian girls from 10 to 20 years of age, found
that the extent of abdominal movement in respiration did not differ from tbat
of men. The work of Wilberforce Smitb (1890), who took respiratory tracings
from different regions of the thorax and abdomen in men. "women dressed and
corseted in the nsnal manner," and "women hahitually wearing no corset," and
that by Kellogg (1895) supports the conclusion of Mays.
A comprehensive revieiv of respiratory movements is given hy C'ripps
(1924). wbich deals witli the publislicd work up to 1924. In this there are hut
two accounts touching the subject of sex difference, which are sui>i)orted by
quantitative data. These are by Pitz (189B) and Hails Dally (1908). The latter.
who used an orthodiagraphic method, did not examine women wearing un-
98
F. S. COTTON
restricting elothingj so that his results agfreed with i)revions findinji's, that a
lesser degree of diaphragmatie movement is characteristic of females. Fitz,
however, made a special study of groups of men and women, including 35 of the
latter who did not wear constricting clothing. He concludes that "between
girls and women and boys and men there is little or no difference in respiratory
tyiie." Whether his results justify this conclusion will be discussed later.
METHODS EMPLOYED IN PRESENT INVESTIGATION.
As the aj)]ilication of any apjtaratus to thorax or abdomen disturbs the
normal movements, it is desirable to ohtain records by a method which avoids
the use of a constricting band to thorax or abdomen. This is possible by
making a series of measnrements in men and women of the resi)iratory changes
in the centre of gravity of the body in the supine and sitting postures.
Tn an earlier communication on changes in centre of gravity (this Journal,
vol. 8, p. 53) it was pointed out that in the supine position the centre of gravity
moved to and fro as a resnit of visceral displacement during respiration. In
the supine position, movement of the thorax in a vertical direction does not
affect the conditions of e<(nilibrium. In the sitting posture, however, the
thoracic movements during insjiiration produee a caudal disjilacemeut of mass,
which wil! be iudicated by movement of the balance index. Diaphragmatic
movements also contribute to this change, since the abdojninal wall is pushed
a little anteriorly when the diapbragm descends. The extent of centre of
gravity change in each of these two cases may be (piantitatively assessed (see
previous communication) as so many grms. cms. of mass displacement, so that
convenient comparisons may be made.
If we now calculate the ratio of the measurement in the supine posture to
that in the sitting posture, if is dear thttt any decrease in ihe thorncic component
must increase fhe rafio, and vice versa,'^ and if fkese rafios for a serie.'i of men
and women .show a significant differcvcc hefween fhe two sexe.'i we may eonclude
that this is a sexual eharaeterisiie.
For the purpose of further explanatiou of the details of the method,
tracings are given in tigs. 1 and 2 to show the varions types of record obtained.
It will be seen that the effect of increasing the abdominal comitonent of
respiration by augmenting the diaphragmatic movement is to greatly increase
the amplitude of the tracing. Tracing C shows, on the other hand, a lesser
amplitude than normal, although the breathing is mnch deei)er. This shows
that the increase of thoracic movement tends to decrease relatively the height
of the tracing in the supine posture.
1 Tf during the inspiration there ia :\ iiii'itsurnlilc displnconii'iit of portiiiu of tlio fhorax
in the criiiiijil dirt'cfioii, it will slightly rleerease the innnf'r;itor of fhis rotio, which would
merely ciiliiinct' the cliange in a manner consistent with tlic meaning of tlio nitio.
SEX DIPFERENCE TN RESPIRATION
Figure 1.
Showing various types of respiratory tracings obtained by
gravity balance table (supine posture).
of the oeiitre of
A. Triifiiig of normal breathing. B. Tracing taken while tlio same subject was conously making more aiuple diaphragmatic movements. C. Tracing,' of deep breathing,
sciously
ieiiy thoracic.
thoraci
Before measurements ofthe tracinfjs were made, however, it was considered
advisable to take into aceonnt the efPeet of the heart-beat in order to eliminate
a disturbing factor. When the snbjeet bohls tbe breatb, as shown in fi<>. 2, the
heart-beats are recorded separately. Tlie amplitudes of these exenrsions are
not the same for tbe sn|)ine and sittinfr postures, nor is the ratio of these found
to be tbe same in different subjects. Hence tbe res|)iratory variations as
obtained must be measured as j^ross excursions, whereas we are really concerned witb tbe net amplitudes. Since the frequeney of the heart-heat is
several times that of the respiratory variations, we have the equivalent of a
series of qniek, small vibrations superimposed ujton slow, relatively large
waves. Hence it would be sufficiently accurate for our purposes to measure the
gross amplitude and dednct tbe bei^iht of the smaller waves.
A tracing typical of that obtained by means of the balance table, showing
these composite waves, is shown in fi^. 2.
For convenience the ratio of the abdominal to the thoraeic component of
respiration, as measured in this way, will be referred to as tbe ratio Ab/Th.2lt should be emphasized that this ratio does not measure the relative amounts of air
inspired, due to the tlioratic and abdominiil couiponents of respiration.
100
F. S. COTTON
S
Figure 2,
Showing ;i tracing tiiken with the subject snpine:
A, Breathing normally.
B. Hotding the breath.
Part A of the record shows the composite trapiiig of heart beats superimposed upon the
respiratory waves. Part E shows the excursions due to the heart-beat only.
Tbe necessary records for computings the ratio Ab/Th were taken in tbe
following stages:
1. The subject, after resting some ten minutos, after ordinnry laboratory activity climbs
on the balance table, and assumes the supine posture. 2. The balance table is equilibrated
by means of Blidiiig weif^hts attached to the side so as to bring tho writing index about
horizontal. 3. The drum is set in motion and allowed to move slowly for some time, until
the respiratory excursions bei'ome re<hn.'<.'d to a reasonably constant level from their tvpicallv
greater initial extent. Tbia usually occupied about three minutes. 4, The drum is then
pushed on a little by hand to make a break in tbe tracing, and a further tracing taken for
one or two minutes, .'i. The subject is then asked to lioUl the breath for about ten seconds,
wlieu a trju-ing of tbe heart alone is recorded, fi. Tbe whole procedure 2 to 6 is repeated
with less initial deliiy after ii woodeu supj>ort to keep the subject still in the sitting posture''
is placed in position on the balance table. 7. A further tracing is taken of the subject iu
the supine posture, so a.s to eliminate the effect of ajiy jirogressive change that niay be taking
place in the iiienn depth of breathing.
To compute tbo ratio for tbe subject tbe meau net cxcursious (total amjilitnre less aiiiiilitiide of tbe heart-beat) are reckoned from eaeli of tbe two su])iiie
tracings, and the average is then divided by the mean net excursion of tbe
sitting tracing.
In order to test whether variation in tbe thoracic component relatively to
the abdominal component does alter the ratio of these excursions in the
manner predicted, a set of tracings was taken with tbe same subject: (1)
Under normal conditions. (2) With the abdomen constricted by means of a
•'It is found iu practice that essentially the same qnautitative result is obtained with
the subject sitting with the trunk inclined at about H0° to the horixontat as with the subject
sitting bolt-u]iright. As the former position was found to be iinich the more comfortable, it
was therefore adlu-red to throughout the experJTuent.s by the provision of a su])[iorting piece
inclined at that angle. In addition^ two small cushions were provided for the head and
hollow of the back reh]iectively, with the result that the subject always reported that the
conditions were ipiite comfortable.
SEX DIFFERKNCE IN KESPIRATIOK
101
:!', 20 feet lonj; and 3 int-heis \\-i(U', wound tightly round it. Tho Iraeings
ol)tained are .shown in ii^. 3.
Figure 3.
A, B, ;uid (' are lospei-tively the supine, sitting-, aiuJ suiiiiie rt'Sjiiratory triu-ings taken in
that HO(jiieit(-f. A,, B ] , and I', are the correHpoiidiny tr;ic-iiigs taken with a bandage wound
tightly round tliu abdomen of the H b j t
The tracing's sliow lliat Ilie expci'inieiital vednction of the abdomiuid eoni])onent of respiriition. toji'etlier with fin inerease iu Ilie tlioraeie eoniponenT. lias
lirodueed a marked (•lianj>'e in the traeings in the direetion indicated by the
iuilial argument. Now the mean net excursions of A and (' ainonnt to 26-2 mm.,
while that of B amounts to 22-.1. Hence the ratio Ab/Th for the normal conditions = l-lti. The eorres|)oiidinti' measurements for the second series of
tracings are 12-0 mm. and 4t)-U mm. respectively, so that in this case the ratio
Ab/Th = 0-2(i. Thus the increase of the thoracic component at the exjtense of
the abdominal comj)ouent of respiration has profoundly reduced the ratio in
question, as |)redictetl theoretically.
THE CORRECTION XECEHSARY TO BE APPLIED TO THF RATIO
Ab/Th ON ACCOUNT OK TIIE INERTIA OF TIIE SYSTEM.
Althon<i:h it was not atiticipated thai the efPect of inertia would ])rot'oundly
alter the correction Viic-tnrs arrived at by calculation from the data of the
previous paper (this Journal, vol. 10, p. 17), it was regarded as imjiortant to
evaluate these factors as accurately as possible. In order to determine the
effect of this inertia factor by experimental means, a rhythmical to and fro
disj)lacement of mass in the longitudinal axis of the system was jn-oduced so as
to simulate the rhythm of respiration. ThLs was accomplished by having a
small table gramoplione fitted up to carry a horizontal revolving arm. to which
P. S. COTTON
102
a sliding adjustable weight was attached. The revolution rates were from
about 8 to 25 per minute. A light subject was chosen, so that the added weight
of the gramojthone brought the total weight to about the average. When the
subject was placed supiue and equilibrium established, with the writing point
in position, the gramophone was set in motion at a measured rate. The subject
was then reipiested to hold the breath for about half a minute, when a tracing
was taken. The revolving weight ^\•as |)laced at such a distance from the centre
as would give tracings of the same order of magnitude as the respiratory
tracings i)revioTisly fonnd with the human subject.
Tracings were secured: A. With the subject supine, and rates of rotation
of the gramophone 9 to 24 jier minute; and Ii. With the subject sitting, with
rates of rotation from 10 to 2H per minute. The resulting tracings were then
examined, and the height of each individual excursion measured so as to yield
an accurate mean.
The results are shown in curves A and I! in tiy;. 4.
6-0-r
•
»
-
,5-5'
2."2
:£- 4.-0'
3-5-
5"
/o ^
Resfiiration ratt
tS
fgr^moHhovfj
ZO
ZS
ptr Tti'm.
Figure 4.
flic caliiiratioii curves obtained by means of tlie "artificial subject."'
sittinj^ poMturo. B for supine
A for
It will be noted that in tliis instance liiF two curves meet at a point where
the inertia effect is iiracticaliy negligible. Tliis apjmrently conflicts with the
correction factors i-aleulated from the c<]uations of the previous paper, where
SEX DIFFEREXCE IX RESPIRATION
103
it was shown that the amplitude of the tracing in tlie sitting: i)osture may be
predicted to be fireater than that in the su|)ine ])ostiire. The exjtlanation for
this is that the effects of the heart-beat have not yet been considered. When
these are determined, and the net amplitudes plotted, the corrected curves Aj
and Bj are resi)ectively obtained. The inertia eifect on the correction ratio
must be determined by actual measurement of the ordinates of the two final
curves Ai and Bj. Let any ordinate of Aj be called A, and that of Bj be li.
Then since our respiratory ratio is reckoned as Ab/Th, the correction factor
must be calculated as A/B. The correction factor for any given frequency nf
respiration is therefore found by calculating,^ this ratio A/B for that i)articuliir
value of the abscissa.
The data for fi^'. 5 are obtained in thi.s way, so that it is possible to read
off from it the correction factor corresi»ondiiiy: to any given rate of resjiiration.
Figure 5.
Showiug the effect of frequency of respiration on the eoiTtictioii fat-tor for Ab/Th due
ti
to inertia.
All the individual determinations previously made were tlien corrected by
means of this graph, so that it was now jmssible to make one complete group of
all the men and another of all the women.
Before dealing with the final results, evidence must be ofU'ered to shoAv that
the method in its entirety is sufficiently accurate for the jnirpose in hand.
AN ACCOUNT OF THE TESTS ilADE TO ASSESS THE CO.MPETENCY
OF THE METHOD AS USKD^ TO YIELD CONSISTENT RESULTS.
Tho value of the method in attacking the |)resent problem clearly depends
upon its cajiacity to give concordant results on the same individual under
•*Tln8 (listiiictioii is iiifide, since much moro accurate resnlts couhi be obtained by taking
longer tracings, which would, however, greatly increase the tedinm of the measureii'ienta.
104
P, S. COTTON
similar conditions of rest. In this eoiiiieetioii it is i)ossibU' for two varieties of
error to affect the final result:
1. Variations due to the experinientfti i)roeedurp or due to some
in the subject on different occasions. 2. Errors in obtaitiiiig the re<iuired ratio
by measurement of auy (jivcn traein^r
The second point will be dealt with first. Even a brief ex|)erience in
resi)iratory tracinji's is suffifient to show that quite considerable variations in
the aiii]>litu(le of iiulividuai excursions are common, so that it is a matter of
jtidgment, wlicii a <riven rnu-infi' is taken, to determine the tnean excursion by
means of a reasonable number of measurements. As |ireviously explained, it
was endeavoured to obtain the tracings in question after the typical preliminary decrease had oeuurred. In general, some 20 to 40 excursions were recorded
iu each tracing. The |)rocedure adojited was to inspect the tracing and to pick
out the most uniform portion covering an extent of some 15 to 20 waves. The
mean amplitude of these was then determined by measurement, and reduced to
net value by deduction of the mean excursion of the heart-beat, which itself
offered no difficulty.
To assess this error a set of tracings was taken and measured, and then set
aside, care being exercised not to mark them in any way. The next day they
were again measured, and the second series of results tabulated. The two sets
of completed tneasurements were then compared. These are shown in parallel
columns iu Table 1.
1.
llic Hffiiills of l>iiplli-(ilf M('ii,si(r(:tiirHt.-< nuKlc o}i Differenl
on llic same scf of Vnmarked
Days
Tracinys.
The cak'uhitcd vjihiea !ire the ratlins Ab/Th foi' men.
First
Second
Diff'ereiict'
Measuremfut.
L.L.B.
1-80
0-04
1-76
•
1-82
H.M.F.
1-75
0-07
R.H.
i-r)2
1-53
0-01
E. McM.
1-57
1-58
0-01
H.R,K.
1-19
1-20
0-01
.I.J,M.
1-41
1'27
0-14
K.V.S.
1-24
1-25
0-01
Meiui
1-47
1-47
0-041
Ki'(nii the table it is seen that the mean error of jitdgment phis measurement amounts to an average of about 3 per cent.
In order to test the first point a series of (itTi)lieate tracings were obtained
in tbe case of a series of subjects on different days. The results are set out in
Table 2.
SEX DIFFERENCE TN RESPIRATION
105
TABLE 2.
Showimj the Consistency of Duplieaff Mea.Hurements itiatlc tipoii a Group
of I'J Women on Consecutive Days.
Ratios of Ab/Th,
First
No. of Subject. Deteriniuation.
1-26
1
0-iU
3
l-0'2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
X8
19
Mean
]•!(!
1 • (i,S
l-;t4
1-29
1-08
1-5G
0-96
1-44
0-84
1-02
1-20
0-98
1-02
1-49
1-20
1-20
M9
Second
Dc'turniination.
1-32
0-99
1-04
1-34
1-65
1-36
1-39
0-99
1-70
1-05
1-21
0-77
0-99
1-21
1-31
1-05
1-21
1-16
1-16
1-20
Differej
0-OG
0 •();•)
a-02
0-lN
—0-03
0-02
(l-ll)
—O-n!l
0-14
0-0!)
—0-23
—0-07
—0-03
—0-01
o-;i;!
o-o:i
—0-2S
—0-04
—0-10
0-10
From the last eohuiiii of the table il is seen that tlie mean absolute error
(irresjieetive of si<rii) is O-IO, i.e., about 8 per eent. This means that, ineluding
all eri'ors. it is ])ossible to obtain a (]Ufintitfitive estimate of the type of respiration in any o;iven snbject correct on an average to about 8 per eent, on oue
examination.
It is therefore submitted that if the nuniber of observations be made reasonably lar^-'e we have in the present method a means of testing for even small
differences in the (juantity measured in the case of different groujjs of subjects.
THE RESULTS OiJTAIXED JX_ TilE CASE OF GROUPS OF :\IEN
AND OF WOMEN.
The men were all medieal students, mostly between 18 and 21 years of ajre.
The ^\'omen were all university students, or teachers in traiiiinfr, ranginp; from
17 to 21 years of ag'e, witb the exception of some three or fonr, who were rather
older. The elotliin<i' was universally of the non-eonsti-ictinir tyi)e.
The grouped results ior botli sexes are set out in Table 3.
F. S. COTTON
106
TABLE 3.
Showing fhe Ratios of Ab/Th obtained in the case of Various Groups
of Men and of Women.
Men.
Group No.
No. of
Subjects,
1
2
3
4
5
Mean.
1-50
1-48
1-51
1-45
14
11
30
31
—
86
Total or mean
Women.
No. of
Sul)ject8.
Mean
1-29
1-19
1-26
1-29
1-24
1-24
26
26
14
13
13
92
—
1-49
The table shows quite a satisfaetory eonstaney for the group means, tho.se
for the men being ajjparently of an order of magnitude quite distinct from
those of the women.
The values for the groups of men and of women are ijlotted as frequency
curves A and B in fig. 6.
•60
-90
120
1-50
1-80
^10
Figure 6.
Frequency curves for the (•oniplcte seri(?s in eaeli sex. A iiieu, B women.
The lines M and AV are placed respectively to mark the mean vahies for
each series. It is evident from the curves that there is a distinct sbift in the
case of the women towards the lower ratio of Ab/Th, although overla|)i)ing
occurs. This gives evidence of a greater thoracic component of respiration in
the ease of the women. The statistical data necessary to determine Avhether
this difference is a real one, in terms of probability, are set out in Table 4.
SEX DIFFEREN'CE IX REyPIRATION
107
TABLE 4.
Statistical Values for fhe Ratio Ab/Th for the Complete Groups of Men
and of Women.
Mean
P.E. Mean
a.D
CoeiilicieJit of Variation
Lower Quitrtile
..
Median
Upper Quartile
..
P.E
Total No. of Subjects
..
..
..
..
Men.
1-49
O-Ol^l
0-295
19-8%
1-20
1-44
1-59
0-19
86
Women.
l-:^4
0-021
0-31
24-8%
0-96
1-29
1'41
0-22
92
It will be seen from tbe table that tbe ratios for the men are rather more
uniform than those for the women, as sbown by the lower eoeftieient of variability, 19-8 per cent, for the men, as against 24-8 per cent, for the women.
Tlie rest of the statistical values, on tbe other hand, show a closer api)roxiination. The P.E. of the mean is seen to be 0-021 in botb cases, indicating that
there are equal odds that tbese values are within 0-021 of the correct figures.
This would imiily that the difference between the two groups is quite definite.
To apply the orthodox statistical test for the reality of this difference
between the groujjs, we note first tbat tbe difference between the means is 0-25.
Now the P.E. of this difference is given by the expression
P.E. (difference) = ^/{i)-021)-'^ + (0-021)^ = 0-029.
Hence the ratio of the actual diff'erence between tbe means to the P.E. of
0-25
that difference =
.^ = 7 - 9 , whence from the tables of probability it may be
seen that the odds against such a diff'erence bet\veen tiie two groups occurring
by chance are more than ten million to one.
In several instances, where previous workers had examined women wearing constricting dress, distinct differences in the tracings were reported when
the dress was loosened. Although in the present series of subjects the dress
was of the non-constricting type, it was considered imi)ortant to determine
when any such difference occurred in the tracings when the dress was
thoroughly loosened. To this end some 22 of the women ^\'cre examined in this
way. The mean ratios for Ab/Th were foimd to be 1-21 before and 1-18 after
complete loosening of tbe dress. This difference is small, and is readily shown
to be in accord witb the variation of sampling. Hence we conclude that the
dress worn by this <^rou[> of women did not aff'ect their normal values for
Ab/Th, so that tbe descrijition of the grouj) of women examined, as wearing
unconstricting dress, is quantitatively confirmed.
Since tbe (juestion as to wliethei' Ilie ratio Ab/Th is affected by physical
training has an important bearing on tbe reality of the sex difference recorded
108
F- B. COTTON
above, the data were examined from this point of view. The subjects of eaeh
sex were divided into a less athletic and a more athletic groui>. The mean ratios
were then found, for the women, less athletic groui) 1-30 and more athletic
group 1-27, and for the men, less athletic group 1-46, and more athletic group
1-49. These differences are iu accord with the errors of sam])ling, so that the
ratio in ijuestion is not a function of the degree of athletic training. This
result supports the conclusion that the respiratory difference observed is a
true sex difference.
In comparing these results with those (luoted in the introduction it shoukl
be empbasized that the most systcmafic set uf (juonfitativc ilata on ihis question
that the mriter cari find are those of Fifz, whose data will now be examined in
detail to discover how he arrived al the opposite condusion.
The method of Fitz was to take simultaneous tracings from the most freely
moving regions of abdomen and thorax respectively, and by measuring the
excursions of the traciugs in eaeh instance, to compute the ratio in tbe latter
case to that of the former, as Th/Ab. Hut Fitz's tables show so great variatioii
in these ratios as to suggest that they are affected by exjjerimental error. In
the case of boys the minimum ratio is O-G and the maximum !)-43, and in tbe
case of the women with unconstricting clothing the minimum is 0-0 and the
maximum 8-18. The other series show similar degrees of variation between
the smaller and larger values obtained. Fitz did not examine his data statistically. He did not even determine the mean value for his groups. The complete
data are not available for comi)arison between the men and the unconstricted
women. In the tables, however, are shown the proportions of ratios between
certain ranges for men, boys, ajid uncoustricted women. These are given in
Table 5.
TABLE 5.
Giving the Pereentages of Cases of Men. Boys, ami ['ncouslrictcd Women
between Certain Ranges of Ratio Th/Ab.
1
Kiitio ot Th/Ab
Men
Boys
Uni-oiiHtri<-t('d
Woiiicn
0-0-0-5
27-4
20-5
2
0-5-2-0
00-9
62-8
58-7
3
Over 3 -11
5-7
S-(i
14-S
The general distribution of values for the boys is clearly intermediate
between that for the men and the unconstricted women.
Hence, if it can be proved that the difference between the groups of women
and boys i.-s real, then so also must be the difference between the groups of
women and men. In <tr(ler to test the matter, the statistical values were determined for tbe tabulated groups of boys and of women. In eaeli case the highest
value was eliminated from the group, sinee the deviation of tbese aberrant
values from the mean were 10-0 and 24-8 times the respective S.D.s, whereas
SEX D I F F E R E N C E TN RESPIRATION
IO9
even a fourfold ratio would suffice to exclude them. The rest of the data was
then examined in the usual way and the contents of Table 6 computed therefrom.
TABLE 6.
Shoiving the Stafisliral Data for the Ratio Th/Ah for Fifz'.-i Groupfi of
Boys and Unconsfricted Women.
Ratio of TL/Ab.
Uneonatricted
Boys.
Women.
0-74
1-18
0-04
0-08
0-35
0-69
Meau
r.E. of Moan
sn
C'ocffiriciit of V;iriiibility
..
Lowoi- Qunrtilp . .
.'.
..
Median
TrpptT Qiiiirtilc
P-E
Nnmber of Siibjpcta . . . .
iT^'/r
0-43
0-58
0-90 "
0-23
34
.^58%
0-48
0-93
1-79
0-6.')
34
Tt will be evident that while there is a substantial difference between the
mean ratios, 0-74 and 1-18 respectively, the hifjh coefficients of variability,
namely, 47 per cent, and 58 per cent., are a stifficient deterrent from the drawing of conclusions by mere inspection, so that a more exact examination must
be instituted before any precise statement can be made. This apparently Fitz
did not do. so that he missed the sifi'nificance of his; own results. Now the reality
of this difference of the two means depends upon their respective probable
eiTor.s shown in the second row of the table.
The P.E. of this difference may be computed as previously, so that it is
equal to V ( 0 - 0 4 ) 2 - ^ (o-O8)2 = 0-089. Hence the reality of this difference
,
1
.,
.- 1-18 — 0 - 7 4
(leitends on the ratio
-QT^J^
= 4-5, whence from the tables of probability
the odds ap'ainst siu-li a ?:ronp difference occurring by chance is rather more
than 1,000 to 1. From this it is evident that the difference between the ^roui)S
of men and nnconstricted women is even m.ore certainly a natttral sex difference. Iletice we may conclude that the only other available (piantitative data
on this subject, which had been adduced to prove the opposite of the conclusion
arrived at iu thi.s paper, in reality helps to contirm it.
SUMMARY.
1. A brief comparison is made of the work of previons investiprators on this
problem.
2. An account is j^iven of the manner in which the meastirement of the
ratio of centre of f^ravity displacements in the snpine and sitting; postures may
no
F. S. COTTON
be used to distinguish relative changes in the thoracic and abdominal components of respiration.
3. Duplicate measurements made on a score of subjects show a mean error
of abont 8 per eent. in the determination of the ratio Ab/Th by this method.
as used. By increasing the length of traeinjis this error may be much reduced.
4. The mean valne of this ratio was found to be 1-49 dz 0-02 in the case
of a g'roup of 86 men, with a S.D. of 0-295, and a coefficient of variability of
19-8 per cent.
5. The corres])ondin(;' values for a fjroii]* of 92 women wearing uueonstrieting clothing were: Mean 1-24 zb 0-02, S.D. 0-31, and coefficient of variability
24*8 per cent.
6. When these data were examined statistically it was shown that this
difference of 0-25 between the grouped results for men and for women is a real
one, with a probability of several millions to one.
7. Athletic and non-athletic subjects were found to exhibit, on an average,
the same ratio characteristic for their sex, within the error of sampling.
8. A special test made on 22 of the women subjects (unselected) showed that
no measurable difference in the mean value of the ratio Ab/Th was produced by
a thorough loosening of the dre.ss. indicating that the clothing originally exercised no appreciable restraint on diaphragmatic movement.
9. A detailed examination is made of the data of Fitz, who has i>nblished
the only ((uantitative data that tho writer can find, from which 1he ojiitosite
conclusion from the jiresent communication was drawn.
10. It is shown from the internal evidence of Fitz's data that lie drew the
wrong inference from his results, and that hiw work confirms the present results
with a iirobability of more than 1,000 to 1.
In conclusion, T wish to express my thanks to Professor II. Whitridge
Davies and to Associate Professor Henry Priestley for encouragement and
criticism, and to Professor A. Mackie, Miss E. Redfern, and Miss E. M. Ilindmarsh for tlieir assistance in connexion with women subjects.
SEX DIFFERENCE IN RESPIRATION
Ul
EEFEEENCES.
Boerliaave, H. (1855): Praelectiones AcademieaeS, 5, p. 144,
Cripps, L. D. (19L'4): The Application of the Air Force Physical Effifiency Tests to Men and
Women, Medieal Researcli Council Spccijil Efport Serifs, No, 84.
Fitz, G. W, (1896): Types of Respiratory Movements, Journ, Expcr. Med., 1, pp. 677-692.
Foster, W. L. (1914): A Test of Physieal Efficiency'', Amer. Phys. Ed. Eev., 19, p. 632.
Halls Dally, I. F. (1908): A Coiitrihutioii to the Study of Eospiratioii, with Speeiat Eefereiice to the Action of tlif Vfrtebra.1 Column and Diupliragm, Proc. Roy. Soc, B 80,
pp. 182-187. (1929): (a) An Inquiry into the Physiologicul Mechanism of Respiration,
Jonrn. Ann.t. and Physiol., 43, pp. 93-114; (b) The Diai>hrafjm in Man-"', St. Bart's
Hosp, E.epts., 44, p, 161.
Hutehinson, J. (1846): On the Capacity of the Lungs and on the Respiratory Functions with
a view to Establishing a Precise and Easy Method of Octi'ctint; Disease by the Spirometfr"', Trans. Roy. Med. Ohir. Roc. Lond., 29, p. 137.
Kellogg, J. H. (1S95): The Influence of Dress in Producing tho Physical Decadence of
American Womcni*, Xursing Rfcorci (London), 15, p. 83.
Mays, T. J. (1887): Enquiriiig into the Chest Movements of the Indian Female-'"', Therap.
Gaz., 11, p. 287,
Smith, W, (1890): Report of the Aniiii.-il Meeting of the B.M.A., July, 1890, Brit. Med.
.Tourn., 2, pp. 843, 844.
Stewart, G. N. (1910): Manual of Physiology, Edition G (London).
''Quoted from Cripps.