J. Soc. CosmeticChemistry,20, 159-171 (March 4, 1969)
Differences Children's
Between Adult
and
Hair HERMAN
BOGATY,
B.S?
$ynopsis•A review--much of it from the anthropological literature--is given on the structural, morphological,and color changesof hair on the head with aging of the subject. Children's hair is on the averagefiner, rounder, lessfrequently medullated, and lighter in color than adults' hair. Scalinessand cuticle-cortex ratio are less certainly related to age, nor is there a consistenteffect reported on changes in chemical and physical properties. The physics of hair color is discussedand some limited experimental data are reported suggestingthat children's hair is more transparent and is less red in hue, with a trend to higher purity. INTRODU GTION
In connectionwith hair color studies,the technical literature on the differences
between
adult
and
children's
hair
was searched.
While
hair
appearance and colorwerethe primaryconcern,informationon the geometry, shape, and chemistrywas also uncovered. Much of the publisheddata foundappearedin literaturenormallynot availableto cosmeticscientists in physicalanthropology and anatomy---andin the periodbetween1925 and 1945. Because the findingsmay be of generalinterest,it wasthoughtuseful to bring togetherin one place the information obtained and to provide a fairly completeset of references againstfuture needs. Somebrief commenton backgroundand terminologymay be helpful. Criteriafor classification of hair haveincludedgrosssize,time of appearance during the life span, and structural variations. Lanugo, or primary hair, is characteristicof the fetal stageof life. It tends to be fine and silky, is nonmedullatedand may be considerablypigmented. Secondary,or vellus, * The Toni Company, Chicago, Ill. Institute, Morris Plains, N.J. 07950.
Present address: Warner 159
I.ambert Research
160
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hair is short,fine, and usuallyunpigmented;the downy underfur of some mammalsand the fine body hair of children and women are probably characteristic.
Some authors restrict the term vellus to such fibers rather
than to any type of scalphair. The tertiary, or terminal,hair is normally considered to be long,coarse,and pigmented,and associated with the mature individual. There is considerable overlapin the varioustypes,and on any givenanimalor in any specificregionof the skin all typesmay be evident, as well as intermediatevarieties. Most anthropologists view the changes that take placeas developmental, wheneverthe transitionfrom the primary throughthe terminaltypesoccurswith increasingage (1-3). A corollary of this view is that the changesdo not occurall at once,and that at any giventime somefractionof the moreprimitivehairsmay be present. Thus, Danforth (1) observes that between6 and 21% vellushairs may still be presentin late childhoodduring the transitionto terminal piliation. DIMENSIONS
AND MORPHOLOGY
Cross-Sectional Size and Shape o[ the Hair
Both of thesecharacteristics have usuallybeen measuredtogetheron the same samples. In an early paper, Wynkoop (4) concludesthat "hair shaft diameterbearslittle or no relationshipto the age of the individual,
though there seemsto be a rough correlation. . . with age group of individuals.... " Examinationof her data indicatesthat the 0- to 9-year agegroupof hair samplesdoeshavesubstantially finer hair than the samples of older groupsmeasured. Trotter and her coworkers(5-7) investigatedthese hair characteristics more thoroughlyby usinga somewhatbetter technique. Some data from these sources,regroupedand rearranged,are given in Tables I and II.
Theseresultsshowthe averageincrease in lineardensityand of cross-sectional area with age at leastthroughthe teen years. There is also a suggestion o[ a modestdeclinewith older agegroups. The ellipticity, as measuredby hair index,doesnot in thesedata correlatewith age. It is emphasized that theseresultsare averagesand that each head containsindividual fibers of a wide rangewith much overlapamongthe age groups. In view of the subject-to-subject variability, the results from two additionalpapersby thisgroupof workersare more conclusive(8, 9). The
hair indexand sizeof a smallgroupof childrenwerefollowedby sampling their headson a regulartime schedulefrom birth throughearly teen age; the data are givenin Table III.
ADULT
AND
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Table
HAIR
161
I
Finenessand Ellipticity of Hair of American Whites" Average Cross-Sectional Number of
Area,
Subjects
Age of Group
0-4 10-14
Square"Units"b
24 40
5-9
42
15-19
31} }
75 73
42 47
35
20-29
Average Hair Index,
56
55
50
77
30-49
100
51
74
50+
44
46
76
•From Trotter (5).
bThepreciseunitsemployedare not clear in the originalpaper. The computedarea is bascd on the microscopescaling device employed. CRatio of minor to major axis.
Table
II
Finenessand Ellipticity of Hair of French Canadians and Americans• French
Age
Hair
of
Group
Canadians
No. of
Subjects
Americans
Cross-Sect.
Index,
Area,
%
Wt./100
mm2 X l0 s
Wt./100
No. of
cm, mg
Subjects
cm,
mg
0-4
46
73
268
3.4
17
2
5-9
36
74
341
4.2
37
3 9
45
10-14
45
74
378
4.7
36
15-19
46
73
425
5.4
38
53
20-29
52
72
422
5.3
55
46
30+
75
72
380
4.7
137
45
9
•After Trotter and Dawson (6).
Table
Cross Section
and Hair
Index
III
of Children
from
B•rth
Hair
Individuals
Age Group, years
Index,
to Youth • Cross-Sect.
Area, mm 2 X lO s
15
I
76
75
16
2-4
7O
237
16
5-9
72
312
11
10+
73
336
•After Trotter et al. (8, 9).
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The relationshipof age and crosssectionis very evidentand is shown consistently by all of the subjects. The averagehair index is not clearly related to maturation, althoughthere is a suggestionthat the hair from the one-year-olds is somewhatrounder. This suggestionis reinforcedby the detailedresultsof Trotter and Duggins (8) giving hair index measurements at one month, sevenmonths,and two yearsfor each of 15 children. In 14 out of 15 casesthe two-yearindicesare lower than either of the younger values, and in 13 of the 15 the seven-month indices are lower than the Table
IV
Medullation and Scale Index as a Function of Age• Proportion of Medullas
Approximate No.
of
Incidence
Individuals of Medullas, Age Group, Years
of
the Broken or Continuous
Typeb
in Group
%
%
0-9
70
40
48
ScaleIndex• 0.24
10-19
30
82
89
0.085
20-29
40
55
67
0.10
30-49
37
80
68
0.11
50-99
60
76
65
0.135
•After Wynkoop (4).
bFourtypesare described: absent,fragmentary, broken(largesegments), andcontinuous. The latter two representmore definite and massivemedullation. •Ratio of scalelength (proximo-distal)to fiber diameter.
one-monthvalues. Interestingly,the averagehair indicesmeasuredon three differentracial groupsof Australianaborigines(7) showa trend to greater flatteningof the hair with increasingage. Medullation and Scalinesso[ the Hair
Somedata on theseaspectsof morphologyare given in Table IV from
data obtainedby Wynkoop(4).
Medullasare lessfrequentlyobserved in
hair sampledfrom youngpeople. Even when presentin youth,the medullas are more often fragmentaryin appearancerather than massiveor continuous as in older ages. The scaleindex measurements also indicatethat larger scalesrelativeto fiber diameterare observedin youngsters' hair. A rough
calculationsuggests that the individualscalesare absolutely,as well as relatively,larger in the 0- to 9-year group. Curiously,the author rejects the conclusion that the incidence of medullation
increases and that the scale
indexdecreases with age. Shebelievesthe correlationis mostlikelywith
ADULT
AND
CHILDREN'S
Table Medullation
mos.
mos.
Hair •
Types of
%
%
MedullasSeen6
mos.
3-5
V
in Children's
No. of Subjects Showing Any Medullas,
At birth
6-7
163
No. of Hairs Showing Medullas,
Age Group
1-2
HAIR
1 yr. 2-4 yrs. 5-9 yrs. 10 q- yrs.
1.0 17 f Scanty and 32 31
extremely fragmented Scanty-broken
34
73
Broken -continuous
48 25 36 31
Most Most
0.4 7.7
Most Most
•Aftcr Duggins and Trotter (9).
bScefootnote,Table IV.
fiber diameter,but her evidenceand argumentin the publishedpaper are not persuasive. Hausman (10) alsoconcludesthat medullation and scaliness are functions of diameterfrom a consideration of a large number of animal species,but he did not studyage per se; Wynkoopwas probablya studentof Hausman and,thus,wasled to the sameconclusion. In a later paper,Hausman( 11) briefly notes "a study of 483 specimensof human head hair taken from individualsrangingfrom 3 hoursto 91 yearsof age" with correlationbei_ng found with diameter of the hair shaft.
A goodreviewof the earlierliteratureand viewson hair morphologyis givenby Noback (12). Dugginsand Trotter (9), in followingthe same group of children referredto earlier, also examinedmedullationin samplesfrom the same heads. Data compiledfrom thispaper (Table V) showthe rapid increase in the incidence of medullation in the first monthsof life; the changein characterof the medullafrom scanty-fragmentary to brokenand continuous is noteworthy. Theseauthorsconcludethat the presence of medullasis a developmental characteristic relatedto age. The sameauthors(13) alsoexaminedthesechildren'shair for scaliness by counting the numberof scales per unit lengthin a directionparallelto fiberaxis. They foundno relationship with ageand very high individual andsamplevariability.A goodsummary of all of the workwith thissingle groupof childrenis givenby theseauthors(14).
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JOURNAL OF THE SOCIETY
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With the groupsof Australiannativesmentionedearlier (7), the frequencyof observedhairs containingmedullasriseswith age and extends into the olderagegroupsas well. No correlationof scalecountwith age couldbe asserted for this group. Fourt (15) interestedhimselfin hair structurein relationto physical propertiesof humanhair. Someof hisfindingsare assembled in Table VI. In the upperportionof thistable,the tendencyfor finerhairsto havea large fraction of their crosssectionin the cuticleis to be noted; in this casethe finesthairscomefrom children. The relationship betweencoarseness and
medullafrequency is alsoshown,with the finechildren's hair beinglessoften medullated. Fourt observes that fiberswith high cuticle-to-cortex ratio tend to be finer and rounder. In a secondseriesof measurements (lower half of TableVI), he sortedtwo lotsof adulthair into fine and coarsesubgroups. His results indicatethat finehair froma givenadultcontains proportionately more cuticle,is lessfrequentlymedullated,and is rounder than the coarse
hair from the samehead. Thesesortingexperiments lend supportto the viewof Wynkoop andHausman referredto earlierthatfineness istheprimary correlaterather than ageper se; nonetheless, vestigialfine hair on an adult head may involvea lack of maturationfrom the developmental point of view.
The actualthickness of thecuticleisslightlylargerfor thecoarse thanfor the fine hair, but not verymuchso. Fourt'slimited data on fiber mechanical
properties showno consistent effectrelatingto age,size,or morphology. Table
VI
Fineness,CuticleThickness,Medullation,and Ellipticityof Human Hair • Cuticle
Area
Average
Sample
CrossSect. Area, mm2X 105
A B
610 448
C
% of Cross Sect.
% of
Fraction Minor/ of Sample Major
Cortex Medullated, Area
16.6 18.9
.... ....
66 32
435
19.0
....
34
2« yr. girl 6mo. boy
325 136
21.4 26.3
.... ....
16 4
RMH--Coarse Fine 146 --Coarse Fine
331 143 568 210
.... .... .... ....
18.7 27.2 16.3 21.8
20 0 91 16
Note: All samplesadult hair exceptwhere noted. aAfter Fourt (15).
Axis,
Cuticle
Thickness, microns
70.1
2.60
91.9
2.42
64.7
2.96
79.6
2.35
ADULT
AND
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HAIR
165
CHEMICAL DIFFERENCES RELATING TO AGE
Cystineand Sulfur Content
An earlypaper(16) describes theresults of elementalanalyses on a variety of hair types. ThisworkreportsCaucasian adulthair to be richerin sulfur and nitrogen and poorer in oxygen content than children'shair. This paperis so poorlydoneand the methodsare so uncertainthat its credibility is very dubious. Wilson and Lewis (17) concludethat no relation can be demonstrated betweencystinecontentof the hair and age of the subject,although"we cannot fail to be impressedby the apparent tendency. . . for cystinein adult hair to be slightlylower .... " More recent work (18) reports measurementsof cystine, cysteine, nitrogen, and sulfur with no consistentrelation with age. In contrast, Japaneseworkers(19) publisheddata which revealedwide variation but sometrend to decliningcystinecontentswith age of the group. To add to the confusionon this point, it might be noted that hair of young,nonhumanmammals(cowsand chimpanzees)reportedly(20) has
lowercystinelevelsthan that of adults. Also,someof the publishedwork (18, 21-23) suggests an association of cystinewith hair color; the more heavilypigmentedfibersusuallyexhibit higher cystinelevels. As will be shownlater, children'shair is lighter in color on the average,and if this secondarycorrelationexists,then one would expect children'shair to be lowerin cystineand sulfur. Thiswelterof inconsistency merelyindicates largeandexpected biological variability. Mostof the workdonehassimplybeeninadequate in methodologyand in samplingscopeto ascertainthe existence of a relationship, if present. Furthermore,it seemsprobablethat factorsother than age--e.g., diet and hormonalpatterns--wouldhave a stronginfluenceon some of these chemical
characteristics.
Fatty MaterialsAssociated with Scalp Hair It is well knownthat changesin oily secretions associated with skin and hair arerelatedto age,e.g.,the increase in secretion associated with puberty. A numberof workers(24, 25) havepublished data indicatingthat children exhibit hair of lower fat content than adults.
The chemical character of
the fat is alsodifferent:cholesterol and cholesterol estersare at higherlevels, and squalene,free fatty acids,and wax estersare at lower levels in cl•ildren
than in adults. These differencesare undoubtedlyrelated to hormonal effects.
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SOCIETY HAIR
OF COSMETIC
CHEMISTS
COLOR
Changeswith Age It is a commonlyacceptedopinion that hair darkenswith age of the subject,and this view is amply confirmedin the anthropometric literature. Sometypical data obtainedby matchingagainstcolorstandards(made of dyed swatches)for Americanwhites (5) and French Canadians(6) are collectedin Table VII. The trend to darkening with age is clear and seemsto occurmostrapidly in the early years. Similar findingshave been reportedwith all populationgroups: in Virginians,Danes,Swedes,French, Czechs(26), and evenin very dark-hairedAustralians(7). A reviewby Trotter (27) notesmany commentsby otherson this subjectand discusses meansfor describinghair color. A usefullongitudinalstudyon color and agingwas done by Steggerda (28). In thiswork, a seriesof childrenwasfollowedover a 10-yearperiod in Holland, Michigan. Color comparisons were made annuallyby matching againstthe Fischer-Sallerscaleand convertingthe letter designations to numbersfor averagingpurposes. A light blonde corresponds to a low number like one, and a pure black corresponds to a high number like 24. The relevantinformationin thispaper is givenin Table VIII. In substance, the head hair of this group of childrenbecomesdarker by almostone unit
Table
VII
Hair Color as a Function of Age• Percentageof Samplesof American Hair of the Specified Hair Color in Age Group Hair
Color
White-Lt.
0-9
Blonde
10-19
20-29
30-49
50-79
19
3
0
0
0
Blonde-Dark
Blonde
61
44
35
25
16
Brown-Brown
Black
20
53
65
75
84
Percentageof Samplesof French-Canadian Hair of the Specified Hair Color in Age Group Hair White-Lt.
Color Blonde
Blonde-Dark Blonde Brown-Brown Black
0-4
5-9
10-14
15-19
20-29
30-89
15
3
0
0
0
0
50 35
22 75
4 96
2 98
2 98
3 97
Note: A small number of red colors have been omitted in computing the percentages in
this table. Only pigmentedfibersread by the authors;i.e., senilegray not considered. •After Trotter (5) and Trotter and Dawson (6).
ADULT
AND
CHILDREN'S
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167
with eachyear of agefor the agesof 6 to 18. No significantsexdifferences were found.
Curiously,the basisfor the changein color is hardly discussed in the literatureexceptasthe comment,"adultsappearto generatemore pigment" not a very satisfactoryexplanation. In view of the apparent continued changewith time overthe full life spanof the individual,a specifichormonal basisis unlikely.
Physicaland MorphologicalEffects on Color
The appearanceof hair depends,of course,on the opticalphysic;of thc situation--thenatureof theincidentlightandthewayit i; reflected,absorbed, and scatteredby structuralclementsof the fiber and by the geometrical arrangements of the hairs as a group. On the latter point, it is a fact of commonexperiencethat a neatly parallel array of fibers is conduciveto highlusterand brightness if the anglesof the incidentlight and of the eye are properlydisposed; a tousledheadof hair is generallydull in appearance. Somefactson thephysics of hair color,followingtheviewsof Garn (29), may be instructivefor generalbackground. Light that fallson hair is absorbed to a largeextent(70-95%), a small amountis transmittedthroughthe fiber, and from 2-20% is reflected--the lastbeingmostimportantin thehair'sappearance.The reflected light has two components: (a) that reflectedfrom the surfaceof the fiber, and (b) that re-reflected afterabsorption.The surface-reflected light is planeTable
VIII
Hair Color as a Function of Age• Mean
Age
"After Steggerda(28).
Hair
Color
No.
of
Cases
6
5.5
80
7
6.4
178
8
7.6
224
9
8.7
218
10
9.2
246
11 12
10.2 11.1
267 285
13
11.9
304
14
12.5
307
15
13.5
302
16
14.3
219
17
15.2
128
18
15.7
43
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CHEMISTS
polarizedand contributes to the senseof sheenor gloss;smoothcoatings like oilsincreasethe mirror-likereflectance,and particulatedepositssuchas dirt, detergent residue,or hair sprayparticlesdecrease it. A smoothcuticle and a regularcrosssectionlead to maximumreflectance.Greaterscaliness and the presence of lateralridgesalongthe shaft (saidto be presentin some Negrohair) or a crenulated, irregularcross-sectional shaperesultin a more diffusereflectionpattern. The reflectedlight has the samespectralcharacteristics as the incidentlight--"the hair shineswith the samecolor as the illuminant"--and
thus the tonal characteristic
of the innate
hair
color is
diluted.
The absorbedlight that is re-reflectedis selectivewith respectto wavelength. The maximumabsorptionis in the near UV, about 400 m/•, and the minimumabsorptionis at 700 m• and beyond. In the visibleregion,the curve of reflectancewith wavelengthis quite linear over the range of 400700 m/•, with a slightupward curvaturefor reddishtone hair (30). Other things being equal, two pigment characteristics influence the reflectivity after absorption: the size of the pigment particlesand their densityof distribution. These factors plus the depth of the pigment bed--i.e., the lengthof the absorptionpath--affect the color. Darkeningwith aging may be related to the larger diameterdiscussed earlier, but there is alsoevidence for increasein sizeand numberof pigmentgranulesas well. A smallfractionof light transmittedthroughthe hair exhibitsa different spectrumfrom that for absorptionand reflectance;it is redder due to scatteringby the pigment granules. Since the incidenceof medullation increases with aging,scatteringfrom thiscausewouldbe expectedto increase and to resultin reddeningof the hue with age. It may be desirablehere to sketchan over-all basisfor the existenceof various kinds of natural
hair color.
Color in hair is producedby pigmentparticles(brownish-blackmelanin granules)dispersed in a clear transparentmatrix of hair keratinsubstance. The principal differencein the appearancewith respectto blondnessor brownnessis a consequence of the number of pigment granulespresent. A high densityof pigmentleadsto the appearanceof brown or dark hair and a low densityof pigmentto blonde. An analogous situationis seenin
screenprinting,wherethe densityof blackdotson a printedpageaffectsthe visualappearance of darkness or lightness.It seemsreasonable to suppose that productionof melanin pigment increaseswith age, and thus more granulesper fiber are presentin olderpeople. in additionto the melanotic brownpigment,theremay alsobe present a muchmorediffuselydispersed or "soluble"red-goldstainthroughout the
ADULT
AND
CHILDRENS'
169
HAIR
cortex(11, 27). The presence of the diffusered materialgivesrise to reddishtonesvaryingfromtrueredsin the absence of muchmelaninthrough strawberryblonds,chestnutbrowns,to reddishblacks. With the diffuse red component absent,ashand drabhair coloris seen,tendingto the blueblack as the melanin granule contentincreases.Fleschet al. (31, 32) have discussed an iron-containing nonmelaninpigmentfound in red hair. With regardto thesubjectof agingandhair appearance, the morphological changesare likelyto influencethe modeby whichlight is reflectedon the hair and henceits appearance. If "young"hair exhibitsa lowerdensity
of melanin,islessfrequently medullated, andis composed of a largerfraction of nonpigmentedcuticle, one would expect children'shair to be more transparent than adults'. This mightbe construedas givingchildren'shair a quality of depth, softness, and transparency. Some measurements with the Den Bestereflectometer(33), which can partition the light reflected from the surfaceand internally, are consistentwith this speculation. In Table IX, data are givenfor hair taken from four peopleat different ages. The columnheaded"Transparency"givesthe ratio of light reflectedafter penetratingthe hair to that believedto comefrom the hair surface. The transparencydoesdecreasewith age for all four subjects. The pigment densitymay be expectedto affect the hue, sincemelanin is brown. Thus ageshouldincreasethe reflectancein the lower wavelengths. The data in Table IX showthat the dominantwavelength,computedfrom tristimulus values,increases slightlybut consistently with age. Thus, younger hair might be thoughtof as coolerand calmerin appearance,i.e., lessred. Table
IX
Reflectometer Measurementsof Hair of Individuals at Several Ages Hue,
Subject Lavonne
Lynette
Becky
Vivian
Hair Color Blonde
Reddish-Blonde
Brown
Black
Age
Transparencya
Dominant Purity, Wavelength %
5
1.26
578
17
10
1.12
581
20
10
1.05
580
51
14
0.69
584
28
3«
0.76
579
24
7
0.66
585
20
8
0.85
589
20
21
0.55
604
11
"Ratio of rcfiection after passagcthrough hair to that reflected from the surface.
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CHEMISTS
The significance of the purity valuesgiven is not clear. The data suggest a trendto lesspurity with age,purity beingthe degreeof closeness with which a colorresembles a true spectrumcolor. Low purity colorsare closerto white, gray, or black, and thus youngerhair may be more truly colored,lessdrab, perhapsfrom the smalleramountof pigmentpresent. (ReceivedAugust 1, 1968) REFERENCES
(1) Danforth, C. H., Hair, Amcr. Med. Assn.,Chicago,II1., 1925. (Out of print.) (2) Garn, S. M., Types and distribution of hair in man, Ann. N.Y. Acad. Sci., 53, 498 (March 27, 1951). (3) Montagna, W., and Van Scott, E. J., Chap. 3, in Montagna, W., and Ellis, R. A., The Biology of Hair Growth, Academic Press,New York, 1958. (4) Wynkoop, E. M., Study of the age correlationsof the cuticular scales,medullas and shaft diameters of human head hair, Am. J. Phys. Anthropol., 13, 177 (JulySept., 1929). (5) Trotter, M., The form, size and color of head hair in American whites, Ibid., 14• 433 (July-Sept., 1930). (6) Trotter, M., and Dawson, H. L., The hair of French Canadians, Ibid., 18• 443 (Jan.-March, 1934). (7) Trotter, M., Duggins, O. H., and Setzler, F. M., Hair of Australian aborigines,Ibid., U.S., 14, 649 (1956). (8) Trotter, M., and Duggins, O. H., Index and size of hair of children, Ibid., 6• 489 (Dec., 1948). (9) Duggins, O. H., and Trotter, M., Medullation in hair of children, Ibid., 8• 399 (Sept., 1950). (lO) Hausman, L. A., Recent studies of hair structure relationships, Sci. Monthly, 30• 258 (1930). (11) Hausman,L. A., Applied microscopyof hair, Ibid., 59• 195 (1944). (12) Noback, C. R., Morphology and phylogeny of hair, Ann. N.Y. /lead. Sci., 53• 476 (March, 1951 ). (13) Trotter, M., and Duggins, O. H., Cuticular scalecountsof hair of children, Am. ]. Phys. Anthropol., U.S., 8, 467 (Dec., 1950). (14) Duggins,O. H., and Trotter, M., Changesin morphologyof hair during childhood, Ann. N.Y. Acad. Sci., 53, 569 (March, 1951). (15) Fourt, Lyman, private communication;unpublisheddata. (16) Rutherford,T. A., and Hawk, P. B., A studyof comparativechemicalcomposition of the hair of different races,]. Biol. Chem., 3, 459 (1907). (17) Wilson,R. H., and Lewis, H. B., The cystinecontentof hair and other epidermal tissues,Ibid., 73, 543 (1927). (18) Clay, R. C., Cook,K., and Routh,J. I., Studiesin the composition of humanhair, J. Am. Chem. Soc., 62, 2709 (1940). (19) Koyanagi, T., and Takanohashi,T., Cystinecontentin hair of children, Nature, 12, No. 4801, 457 (Nov. 4, 1961). (20) Block,R. D., and Lewis, H. B., The amino acid contentof cow and chimpanzee hair, J. Biol. Chem., 125, 561 (1938). (21) Flesch,P., The cystinecontentin coloredand white hair of mottledanimals, J. Invest. Dermatol., 14, 157 (1950).
ADULT
AND
CHILDREN'S
HAIR
171
(22) Wolfram, L., and Lennhoff, M., The cystinecontent of hair: fiber-to-fibervariation, Textile Res. J., 37, 145 (1967). (23) Ogura, R., Knox, J. M., Griffin, A. C., and Kusuhara, M., The concentration of sulfhydryl and disulfide in hmnan epider•nis,hair and nail, J. Invest. Dermatol., 38, 69 (1962).
(24) Eckstein, H. C., The cholesterolcontent of hair, wool, and feathers,J. Biol. Chem., 73, 363 (1927); Nicolaides,N., and Roth•nan, S., Studies in the che•nical cron-
positionof hmnanhair fat, J. Invest. Dermatol.,19, 389 (1952); Washburn,S. L., and Liese, G.J., The cholesterolcontent of hu•nan sebmn,J. Lab. Clin. Med., 41, 199 (1953). All in Rothman,S., Physiologyand Biochemistry o[ the Skin, University of Chicago Press,Chicago, II1., 1954.
(25) Nicolaides,N., Chemicalcompositionof hmnan hair fat, y. Invest. Dermatol., 21, 9 (1953).
(26) Bean,R. B., Hair and eye colorin old Virginians,Am. J. Phys.Anthropol.,20, 171 (1935).
(27) Trotter, M., Classification of hair color,Ibid., 25, 237 (1939). (28) Steggerda, M., Changein hair colorwith age,f. Heredity,402 (1941).
(29) Garn,S. M., Humanhair: Its composition, anatomyand distribution, Ph.D. thesis, Harvard University, April, 1948.
(30) Gardner,B. B., and MacAdmn,D. L., Colori•netric analysisof hair color,Am. ]. Phys.Anthropol., 19, 187 (1934).
(31) Flesch,P., and Roth•nan,S., Isolationof an iron pigmentfrownhmnanred hair, J. Invest. Dermatol., 6, 257 (1945).
(32) Flesch,P., Esoda,E. J., andKatz, S., The iron pigmentof red hair and feathers, Ibid., 47, 595 (1966).
(33) Den Beste,M., A new reflectometer, in preparation.
