(Received November 7, 1969; revision accepted for publication February 27, 1970.)
This project was supported by a grant from the U.S. Office of Education ( Regional Office IX), project No. OEG-9-9-140067-0017-057CS. It was carried out at the Department of Pediatrics of Stanford Uni-versity School of Medicine while the author was on Sabbatical Leave from the Hebrew University of
Jealem.
ADDRESS FOR REPRINTS: The School of Education, The Hebrew University, Jerusalem, Israel. PEDIATRICS, Vol. 46, No. 2, August 1970
DEVELOPMENTAL
PATTERNS
OF
STATIC
BALANCE
ABILITY
AND
THEIR
RELATION
TO
COGNITIVE
SCHOOL
READINESS
Reuven Kohen-Raz, Ph.D.
From the Hebrew University, of Jerusalem and the Department of Pediatrics, Stanford University School of Medicine, Stanford, California
ABSTRACT. Developmental patterns of static
bal-ance ability in children at ages 5 to 9 years were assessed by using a technique of electronic atax-iametry, consisting of the measurement of body
weight displacement by pressure transducers,
mounted to four footplates, each to bear one heel or toe part. The obtained fluctuation and weight displacement scores for various postures, none last-ing more than 20 seconds, turned out to correlate significantly with teacher’s evaluation of school readiness, basic arithmetic skills, and reading achievement in samples of normal school children (one kindergarten, two first grades, two second grades, and one third grade; total, 206).
Girls who were prococious in static balance ability
in relation to boys tended to show higher within sex
group correlations between equilibrium control and
school and reading readiness. A sample of 33
undifferentiated educationally handicapped pupils at age 9, having a generally but not significantly lower static balance ability in postures with oc-cluded vision, was efficiently divided by
ataxiamet-nc scores into balance-impaired and balance-un-impaired subjects.
The study seems to throw new light on the role of maturational and organic factors in the etiology of learning difficulties in normal and educationally handicapped children at the primary grades. Pediat-rics, 46:276, 1970, STATIC BALANCE, SCHOOL
READ!-NESS, MOTOR DEVELOPMENT, EDUCATIONALLY
HAND!-CAPPED CHILDREN, ATAXIAMEThY, STATIC BALANCE
ABILITY.
S
TATIC balance ability is essentially the capacity to maintain the typical hu-man, upright posture under various(
some-times stressful)
circumstances without any overt displacement of the feet and without any other part of the body (besides the feet) touching a supporting object or sur-face. This function must be differentiated from keeping equilibrium while in motion,as for instance when walking on a rail or
climbing a tree. Actually, factor analysis has repeatedly shown that “static” and “dy-namic” balance are represented by different factors of motor abiity.l
The anatomical, physical, physiological, and psychological aspects of the human body’s static equilibrium have been
exten-sively investigated by scientists from
van-ous disciplines, applying different methods and techniques. Medical research has tried to elucidate many neunophysiological and
physical factors involved in the act of
standing, namely, muscle activity,2’3 the
lo-cation of the center of gravity and its dis-placements, the function of the vertebral column, the constellation of physical forces acting upon the ankle joint,6 the influence of sex and aging,7’8 neurological correlates,9 the mechanisms of the foot,’#{176}reflexological aspects, the effects of temperatune,12 and
so forth. Recently aerospace and naval
medicine are giving increasing attention to problems of static balance.13
Psychological and educational research
(
and in the latter domain especiallyre-search in physical education) has been
mainly concerned with strictly behavioral aspects of static equilibrium control. Some
early publications on this subject date back
ARTICLES
by Oseretzki’5 and by Sloan.16 Norms for adolescents and young adults have been re-cently provided.T’1721 The main objective of psychological and educational research
has been the establishment of
developmen-tal norms in order to predict physical per-formance and success of physical training.
Recently systematic attempts have been
made to investigate the impairment of
bal-ance in retarded and handicapped
chil-dren.19’22
Several methods of measuring static bal-ance ability are described in the foregoing literature. The simplest and most straight-forward way to assess equilibrium control is to measure the time of maintaining a cer-tam posture without moving the feet or tak-ing resort to support. This method is used in developmental tests of motor ability.
7,15,16,18,19,21 Although apparently reliable in
older subjects, the relatively short timed pass/fail scores are of questionable
reliabil-ity in children under the age of 6 years.
This approach has the additional disadvan-tage of measuring the incidence of failure instead of assessing the patterns of
perfor-mance. More sophisticated methods are
based on the use of devices called ataxiam-eters or statometers. The principle of these methods consists of recording body sway, transmitted by means of a stylus attached to the head, hips, or back or mounted to
foot-plates.6’23’2 A peculiar machine has been constructed by Miles25 who used a head-piece attached to four mechanical count-ers, one for each direction of sway
(
for-ward, backward, left, and right) . A rathercomplex statometer, combining a
mechani-cal and electronic output system, has been
employed by Akerblom.4 All these devices
have been used foremost in laboratory
ex-periments with adults, whereas children in field settings were examined by the simpler methods of presenting timed test items.
OBJECTIVES
OF PRESENT STUDY
Whereas the foregoing research is
fo-cused on intradisciplinary issues in the
do-main of anatomy, neurophysiology, physical education, and so forth, it was the purpose
of this study to examine the eventual role of static balance ability as a bridging function between subcortical response systems and higher mental processes, and thus to widen the basis for interdisciplinary approaches to cognitive development. This research ob-jective was based on developmental
theo-ries, such as formulated by Rothschild,26
Schilder,27 Werner and Wapner,28 Uexkull,29 Rey,3#{176}and Piaget,34 indicating that the abil-ity to keep static equilibrium is related to consciousness and cognitive control. Fur-thermore, observations of kindergarten children and first graders, as well as results obtained by traditional motor tests, have shown that static balance ability develops
intensively between the ages 5 and 9.
Therefore, it was assumed that a relation-ship may exist between the latter and cog-nitive abilities, necessary to attain school readiness and to acquire basic scholastic skills in reading and arithmetic. However, it was obvious that, for the purpose of such an investigation, a method must be found which would measure equilibrium control not in terms of failure scores but in the form of objectively scorable performance patterns.
METHOD
In order to provide such measures, an electronic ataxiameter was constructed,
consisting of four footplates (for each heel and toe respectively), equipped with trans-ducers which were sensitive exclusively to vertical pressure. The electronic output of these transducers can be recorded by any conventional four channel registration ap-paratus and is objectively scorable, either by visual inspection or by computer tech-niques.
This output consists essentially of four waves, which depict the patterns of weight displacement over the four footplates, while the sum of deviations from the four base
lines is constant and equals the body
weight of the subject. Specimen of left heel waves, while standing on the left foot, are shown on Figure 1.
and lights which are operated while the child tries to control his balance, is pro-vided. The equipment is portable and can be easily set up in schools where 20 to 25 children per day can be conveniently exam-ined. For a detailed description of the ap-paratus and method see Final Report.33
The ataxiametric test battery consists of the following postures, each to be kept for 15 to 20 seconds
(
henceforth they will be abbreviated as indicated in parentheses):(
1)
Standing normally with eyes open(
NO). The plates are placed one beside theother, without any space left between them.
(
2) Standing on left and right foot re-spectively, with eyes open (OF).(3
)
Standing normally, blindfolded(
NC)
. Same posture as point 1.4 58
(4
)
“Modified Romberg” Position, eyes open(
MO) . This posture is midwaybe-tween normal standing and the Romberg
(
heel-to-toe) position, in that the heel of the right foot is placed to the right side of the left toe.(5) “Modified Romberg” Position, blindfolded (MC).
(6) Romberg Position, left foot behind, eyes open
(
RO). This is the traditional pos-ture used in routine neurological examina-tions. The right heel is now placed in front of the left toe.(
7)
Romberg Position, left foot behind, blindfolded(
RC).Three types of scores were elaborated, namely,
(
1) a
Fluctuation Score, indicating the sum of amplitudes per second, relative58
55
55
46
40
‘-‘. 31
27
Fic. 1.Ataxiagrams of left heel while standing on one foot. Duration of record
is 15 seconds. The left portion of the graph shows eight normal girls of Grade III ( Sample A) showing a correlation of .94 between reading and static
to the total body weight; (2) a Synchrony I 2 I
Score, measuring the constancy of even
weight placement on the two footplates . .
#{149}B’-I “ “ I I
placed in the rear
(
the two heel plates in I- , ‘p p
the normal standing position and the heel , In.,
and toe plate of the rear foot in the Rom-
I
,, ,
. .-
Ibert positions )-the Synchrony Score thus
I
Irepresents a measure of forward-backward
I
Cl) Isway; and
(
3) a Weight Displacement .f- I.4.-Score, indicating the average percentage of
I
“ ‘ ‘ Iweight per second concentrated on the rear
I
cI
cn I 2foot in the Modified Romberg Position. I
(
For further details of the scoring method _,# ‘ , #{176}0 I Iand system, see Final Report.33)
Not all the theoretically possible scores ca
-
2were elaborated for the purpose of the
I
present study because of economy of time . _.e, ,* 4- ,t-
-
G4-and because some of them showed a low I ,, ,4 ‘ ,4
-B
test retest reliability, among them all scores II fi .,
relating to postures with the right foot in I ‘ ‘ ‘
Q
z
rear position. Those actually computed are ‘ I
‘ I 2 ‘ :
the following:
I
c) * -p
OF-Sum of the two Amplitude Scores I _oo © Gt- 4
for left and right heel. - I
x
-
-u
NC-Sum of Fluctuation and Synchrony I
Scores of the two heels. x
MO-Left foot in rear position-Weight
E’ I
Displacement Score of left foot. I 2
I
MC-Left foot in rear position-Weight ‘ I u
I II
4’
‘I
ll flDisplacement Score of left foot. ,) I
RO-Left foot in rear position-Sum of - e
-
-.,_cI,o Ca ‘ - -
-Fluctuation and Synchrony Scores of left I ‘
‘3
foot. I a
, 4,. . 4 -p
RC-Left foot in rear position-Sum of
foot.
Fluctuation and Synchrony Scores of left - 1 t) I I
SAMPLE AND PROCEDURE
.
.,.-p ,, I
I
ca-Two independent samples were investi- I “
-
.t, .4, I Igated, designated forthwith sample A (Pi- ‘ ‘ I
lot Study) and sample B (Main Study) .
_;
Sample A was composed of 66 subjects from . c#{176} ‘ ‘ . q
grades I, II, and III of one Palo Alto Ele-
I
I.1I
mentary School. The population of sample
I
B was recruited from two schools of the a ‘ ‘
-
4,. I 2 .‘ ERedwood City School District and con-
p
sisted of 140 subjects from kindergarten I “ ‘ I
and grades I and II
(
breakdown accordin g © .to sex and grade is given on Table I). In Z J
a
been placed in special classes for
Educa-tionally Handicapped (not mentally
re-tarded), were included in the study. Most subjects were Caucasian
(
Anglo-American and Spanish Mexican)
; and a smallminor-ity were Oriental. No Negro subjects were
included according to the original design of the study in order to control eventual racial differences of psychomotor development.
All subjects were tested individually with the ataxiametric method. The criterion van-ables of mental development, school
neadi-ness, and scholastic achievement were
measured as follows: in sample A the
Bond-Balow-Hoyt New Developmental Reading
Tests34 were administered in group form to the three elementary school grades. The
kindergarten children of sample B were
evaluated by means of a Teacher Observa-lion Inventory,35 by an Arithmetic School Readiness Test,36 and on the basis of their scores on the Bender Gestalt and Peabody Picture Vocabulary Tests. All the kinder-garten subjects were tested individually. The first and second graders of sample B
were examined in groups with the Stanford Achievement Tests. In addition, the first graders were given, also in group form, the Metropolitan Readiness Test.
Test-retest reliability of the ataxiametnic method was assessed by reexamining 26 first graders 4 days after their first
ataxia-metric examination.
Reliability
RESULTS
The test-retest reliability of MO
(
.81), MC(
.71),
OF(
.67), and that of the com-posite score MO + OF(
.88)
are satisfac-tory, especially in view of the fact that the experimental time of these items is only 20 to 50 seconds. The reliabilities of NC(
.64),RC
(
.51),
and RO(
.42) are relatively lowbut were considered to be acceptable in the context of an exploratory study.
Developmental Patterns and Sex Differences
As large deflections, fluctuations and low synchrony, which are signs of weak balance ability, will cause a high OF, NC, RO, and
RC score, developmental progress will show
up in their decrease by age. For the
same reason, positive relations between sta-ble static equilibrium and cognition will be manifest in negative correlations between these ataxiametnic scores and mental mea-surements. On the other hand, MO and MC
are Weight Displacement Scores, a high
score indicating that weight is predomi-nantly shifted backwards. As an insecure, unstable posture is characterized by leaning forward, probably in order to prevent the rather dangerous backward fall, high MO and MC scores are supposed to be a sign of good stability. Therefore, they should in-crease by age and their correlations with mental scores are expected to be positive.
Table I shows that the amplitude, fluctuation and synchrony scores of OF,
NC, RO, and RC demonstrate a definite
progress by age, which is steeper and more
consistent in girls than in boys. Further-more, girls are consistently superior in their static balance ability on these four items, although the difference is significant only in five instances. It will also be noted that sex differences conspicuously increase after school entrance
(
from grade one onward). These findings are in accordance with allprevious studies exploring sex differences in
static balance ability.
On the other hand, MO and MC do not show any clear developmental pattern and also no consistent sex differences. The third grade sample is too small to justify the as-sumption of an eventual curvilinear devel-opment in girls. There seems to be a
diver-gence in the development of MO and MC
in boys. MO tends to decrease, whereas MC increases.
Correlations Between Ataxiametric Scores and Measures of School Readiness
and Reading Skills
KINDERGARTEN: As shown in Table II, OF correlates significantly with Teacher Evalua-tion of School Readiness, as well as with two
subtests of the Arithmetic School Readiness
Test, namely Group and Fractions and
281
the Bender Gestalt. The correlation between a composite score OF + RC with Teacher Evaluation reaches the .01 level of signifi-cance.
A striking sex difference shows up in the
relationship between OF, RC, OF + RC,
and Teacher Evaluation. In spite of shrink-age of N and restriction of range
( girls are
evaluated higher on school readiness and are also precocious in their ataxiametric performance),
the correlations within the female sample remain significant but drop substantially in boys.(
See Table III ). For the tabulated correlations in the male sam-ple, see Research Report.33FIRST GRADE: In the first grade of sample
A the total score of the Bond-Balow-Hoyt Reading Test (Lower Primary Level), used as a single criterion variable, correlates sig-nificantly with the composite score OF + MO (Table II).
In the larger first grade population of
sample B, these results are cross-validated in that OF and MO (this time each item by itself) both correlate significantly with the Paragraph Meaning subtest and the Total Score of the Stanford Achievement Test.
Combining OF and MO and adding RO,
the resulting composite score OF + MO + RO correlates with reading at the .002 level
(
Table II ). When sexes are separated, the combined OF-MO-RO score continues to be significantly related to Word Reading,Para-graph Meaning, and Total Score in both
sexes; the relationship is more pronounced in girls
(
Table III).MO turns out to be a good single predic-tor of Stanford Word Reading, Paragraph Meaning, and Total Reading Score in the sex-combined as well as in the female sam-ple.
RO seems to be sensitive to sex
differences in the relationships between ataxiametric scores and school readiness
TABLE II
CORRELATIONS BETWEEN STATIC BALANCE AND MENTAL ACHIEVEMENTS BOTH SEXm
Grade
Sam-pie N Mental Tests
AtariameL nc Scores
OF NC MO RO RC
-
Joinpoite ScoresK A 51
Bender Teacher
evaluation
Arithmetic problems
-6f
-SOt
-8f
-sst -36 (OF+RC)
I B 47
Metropolitan match Metropolitan
number
Stanford Word
Stanford Para. Stanford Total
reading
-4
-SSt
-S7
4S 35f
SOt
-8t
-Sit
-6t
-Sot
-44 (OF+MO+RO)
-44 (OF+MO+RO)
-47 (OF+MO+RO)
I A 26 Hoyt Reading -9 -36 51 -38t (OF+MO)
II A 18 Hoyt Reading -48t -59 -41 -50t (OF+NC+RC)
III A 1 Hoyt Reading -38 -37 (OF+NC+RC)
*
p
approaches .05.t p=.05.
p=.01.
TABLE III
CoIuELATIoss BETW EEN STATIC BALANCE AND MENTAL Aciii EVEM ENTS: Girls
Grade Sam-pie
Menki! Tests Ataxiamet nc Seore$
-OF NC MO RO RC
----
-(‘ouipusite &Scoresj
Bender -35
K A 25 teacher
evaluation -43t -39t -5 (OF+lC’)
Arithmetic
problems -9
I B ‘i3
Metropolitan word Metropolitan
numb. Metropolitan
copy
Stanford Word
Stanford Para. Stanford Total
reading number Stanford Vocab.
-21
-29
- 8
-25
36*
42t 56
59
63
-41t
-4’2t
-31
-26
-34
-44t
40t
-50f (OF+MO+RO)
-58 (OF+MO+RO)
-59 (OF+MO+RO)
I A 11 Hoyt Reading -15 -37 6 5 -9 (OF+MO)
II A 9 Hoyt Reading -‘fl -45 -46 -50 (OF+NC+RC)
III A S Hoyt Reading -94 -68 -88 (OF+NC+RC)
S approaches .05.
t p=.05.
1:p=.Ol.
§Specification of composite score is given in parentheses iiext to correlation coefficient shown in this column.
tests; its correlations with the Match and Number parts of the Metropolitan Readi-ness Test, which are marginally significant when sexes are combined, turn out to be sex specific in that a significant correlation with the Number subtest shows up only in the female sample and one with the Match sub-test appears exclusively in boys. Another sex difference emerges in the relationship of RO with the Metropolitan Word and Stan. ford Vocabulary subtests, the relationship with both tests being conspicuous in girls and absent in boys. On the other hand, in the male sample there is a somewhat higher correlation between RO and Stanford Word Reading.
RC is correlated with the perceptual
Match subtest, a relationship which
re-minds that of RC with the visual-motor Bender Gestalt Test at the kindergarten level. However, this relationship is appar-ent only in boys.
In girls only RC correlates also with the Metropolitan Copy subtest; but, in inverse direction, i.e., higher fluctuation is related to higher mental scores. These inconsisten-cies seem to indicate that the relationships between static balance ability and percep-tual school readiness are either unstable and unreliable or inadequately measured by our present scoring system.
It is of interest that the more complex reading skill, as measured by Paragraph Reading, correlates substantially and
con-sistently with ataxiametric scores, whereas
283 Test which measure predominantly
audi-tory discrimination and the understanding of vocally presented words show generally low and only sporadically significant corre-lations.
(
For tabulated data see Research Report.33)Sco GRADE: At the second grade of Sample A, OF as a single item correlates sig-nificantly with the Total Score of the Bond-Balow-Hoyt Reading Test
( Upper Primary
Level), used again as the only criterion vari-able. The relationships between MO and reading, which were found at the first grades, disappear. On the other hand, NC and RC, although not significantly related as single items, combine together with OF into a composite score of considerable validity, manifest in a correlation coefficient of - .50.
Grade II of sample B shows only one sin-gle significant correlation (r - .31
)
be-tween the composite score OF + RO and
Paragraph Reading of the Stanford Achievement Test
(
Primary II Level).Timw GiwE: The small sample of Grade III of sample A, the only representative of its age/grade level nevertheless shows a con-spicuous relationship between static balance ability and reading achievement (Table II) as measured by the Total Score of the Bond-Balow-Hoyt Reading Test
( Upper Primary
Level). The relationship, however, turns out to be absolutely sex specific, in that in the female sample the correlation reaches the size of - .94 whereas it drops to zero in the
group of boys. This correlation, which is close to a one-to-one relationship, is appar-ent by visual inspection of original data plotted on Figure 1. The latter finding seems to link up with a similar pattern found in the relationship between OF and Teacher Evaluation in the kindergarten sample and in the considerably higher correlations be-tween static balance ability and reading in girls, which appear in the first grade of sample B. These data may lead to assump-tions about possible sex differences in the role of maturational/organic factors in the causation of learning difficulties.
That is to say, it would appear that, at the primary grades, the girls’ lower
scholas-tic achievements would be more probably caused by deficient or retarded organic maturation, whereas the boys’ learning problems would more frequently be the re-sult of environmental and psychogenic conflict.
Ataxiametric Patterns in Educationally Handicapped School Children
The 33 educationally handicapped stu-dents included in this study belong to a large variety of clinical groups, so no gen-eral description of their disturbances can be given.
As can be seen in Table I, the education-ally handicapped girls are definitively infe-rior in their static balance ability when compared to age/grade mates of the same sex and even to those who are 1 year younger. The differences are statistically not significant, which might be due to the smallness of the sample (5 EH girls). It is also striking that the EH girls perform on a considerably lower level than the EH boys, whereas in the normal groups girls are con-sistently superior to boys in static balance. This finding would be in line with our as-sumption, mentioned before, that learning difficulties in girls tend to be more matura-tionally and organically determined than in boys.
As to the male EH, although they tend to be superior in “open eye” items
(
OF and MO), they show a definitively lower achievement on ataxiametric items with oc-eluded vision (namely, NC, MC, and RC); however, the differences are not significant. When data were more closely inspected, the EH sample was characterized by a typi-cal bimodal distribution of ataxiametric scores with extreme positive deviations, in contrast to the normal distribution in the control group. This seems to indicate that, although the ataxiametric scores are appar-ently not detecting significant differences instatic balance ability between normal
bal-ance-not-impaired subjects, which may be of considerable diagnostic and therapeutic significance.
In addition, the balance-impaired EH seem to be characterized by qualitatively deviant ataxiametric patterns which have not yet been quantified and defined by our present, preliminary scoring method but can be readily seen by visual inspection
(Fig. 1).
DISCUSSION
Overviewing our findings, it seems that the most striking and consistent relation-ship between mental and ataxiametric vari-ables is shown by OF. It correlates with teacher observation and arithmetic school readiness at the kindergarten level and with two different, well standardized and widely used reading tests in five independent
sam-pies of first, second, and third graders. RO seems to be functionally close to OF but appears to predict a wider spectrum of scholastic achievements than OF, including numerical and perceptual tasks, besides be-ing sensitive to sex differences in the rela-tionships between balance ability and cog-nition.
MO turns out to have considerable pre-dictive validity, which however is limited to the first grade.
In contrast to the “open eye” items, the tasks involving occluded vision are rela-tively less and less consistently related to cognition in normal populations.
On the other hand, they tend to discrimi-nate between normal subjects and educa-tionally handicapped subjects.
Generally it may be stated that the main
hypothesis has been supported and that
static balance ability as measured by elec-tronic ataxiametry is substantially related to school readiness and reading achievement.
Furthermore, the fact that the ataxiamet-nc performances of 15, 20, and 30 seconds correlate significanfly with achievement tests, which have administration times be-tween 15 minutes to 1 hour (not speaking of the Kindergarten Teacher Questionnaire based on long range observation
)
,
seems toindicate that the ataxiametric scores reflect neurophysiological and reflex-level roots of mental responses. Whereas intelligence or achievement tests predict a certain universe of mental abilities by virtue of the former
being a representative sample of this same
universe, the ataxiametric battery seems to
possess predictive power because it eventu-ally measures basic organic processes un-derlying these responses. If this will be fur-ther substantiated by future research, new
avenues of approach may be laid open to
detect the causal relationships between neurophysiological maturation
(
or learning on neurophysiological level)
and basic mental processes which play an important role in the attainment of cognitive(
and possibly also social) school readiness.Our results also seem to indicate that
be-tween 30 to 60% of learning difficulties at
the lower elementary grades might be at-tributed to organic or maturational pro-cesses reflected by the ataxiametnc scores, which thus might provide clues to discrimi-nate between predominantly emotional-social and neurological-maturational learn-ing handicaps; girls tend to have a stronger disposition toward the latter.
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Acknowledgment
We wish to acknowledge the devoted collabora-lion of Mrs. Noemi Wagner in carrying out this study and the assistance of Miss Margarete Ashly in conducting the ataxiametric experiments. We
thank the school district research directors, Dr. Bruce Keepes and Dr. Leroy Porter; the school
principals, Mr. John Papagni, Mr. Don Johnson,
and Mr. K. McCarthy; and the teachers and the
staff of Hoover School, John Gill School, and Taft School for their efficient cooperation in organizing
the examinations and providing the subjects. We
are much indebted to Mr. Geoffrey Buck,
represen-tative of the N.A.S.A. Biomedical Research
Assis-tance and Utilization Program, who helped and
advised us during the first decisive phases of the program. Thanks are due to Dr. Harry Jennison, Medical Director of the Stanford Children’s Con-valescent Hospital, for his guidance in organizing the study and to Mrs. Lindo Marrachine and Mrs.
D. David Forsythe, who assisted in carrying out our
