Journal of Criminal Law and CriminologyVolume 31Issue 4 November-December Article 12

Winter 1940

Human Hair Studies: General Considerations ofHair Individualization and Its Forensic ImportancePaul L. Kirk

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Recommended CitationPaul L. Kirk, Human Hair Studies: General Considerations of Hair Individualization and Its Forensic Importance, 31 Am. Inst. Crim.L. & Criminology 486 (1940-1941)

HUMAN HAIR STUDIES*

1. General Considerations of Hair Individualization and ItsForensic Importance

Paul L. Kirkt

Human hair unquestionably figuresas a clue or possible clue in a very con-siderable percentage of crimes, particu-larly those of violence, but only slight-ly less in crimes of stealth, since mostindividuals have a greater or less tend-ency to lose hairs unconsciously andat random. It is indeed strange that sotempting a type of evidence shouldhave been so indifferently treated bycriminal investigators. Some criminol-ogists have expressed confidence in

their ability to determine the source ofa hair, but usually without benefit ofadequate study and by methods thatare not generally known. The commonattitude is well expressed by SydneySmith (1) who states, "If a definite

answer is required as to whether a cer-tain sample of hair is that of a certainindividual, the investigator is strongly

advised to refuse to go further than tostate that the hairs are similar". With-out question, present knowledge justi-fies such a statement to a very consid-erable -extent, but to accept this viewfatalistically as the last word on thesubject is as strange as the attitudetaken by many toward fingerprints in

the early days of development of thatimportant branch of criminological

knowledge. To the best of the author's

information, the investigation as to

* These studies were made with the aid of agrant from the Research Board of the Universityof California, and of clerical assistance from the

whether a suspected hair belongs to aparticular person is rarely carried fur-ther than to observe its most obviousproperties, such as its color and itslength, points which are obviously of

very limited value. This is even moresurprising when most criminal investi-gators are well aware of the possibili-ties of distinguishing the animal speciesof the hair, and spare no pains in en-larging, sectioning, and otherwise in-vestigating the hair from this stand-point. This phase of hair study has un-

doubtedly been inspired by such ex-cellent investigations as those of Glais-ter (2), Hausman, (3) and others.

Some investigators (1, 4) go furtherand claim to determine age of humanhair by such methods as measuring therate of solution of a hair root in caus-tic potash. It would seem at least asdifficult to accurately determine the ageas to determine the individuality of thehair, if there is any analogy to otherbodily structures such as frictionridges, or the physiogomy.

While thorough studies of the indi-vidualization of human hair have notbeen reported, the total amount of hairinvestigation which has been publishedis very impressive. Without attemptingto completely review the literature,some of the more recent and outstand-

Works Progress Administration.t Associate Professor of Biochemistry, Uni-

versity of California.

[ 486 ]

HUMAN HAIR STUDIES

ing contributions are here listed. Haus-man (3) has contributed an extensiveseries of papers on this subject, chiefly

from the anthropological point of view.

Trotter (5) has made valuable sys-

tematic studies on human hair and has

reviewed the classification of hair (6)

quite thoroughly, along with an .excel-

lent bibliography. Another recent studyof classification was made by Eddy (7).

Methods of examination of hair have

been discussed by Roig (8), Harvey(9), Fiale (10), Bellamy (11) and

others. General discussions of the for-ensic importance of hair and its study

are included in most books on crim-inology and forensic medicine, includ-

ing Smith and Glaister (12), Soderman

and O'Connell (13), Smith (1), Dan-

forth (14) and other similar references.

Older work which has often been

quoted but is frequently inaccurate and

occasionally misleading is that of Lam-

bert and Balthazard (15).

Since it is a matter of common obser-

vation that an individual's hair is usu-

ally more or less distinct in appearancefrom that of other individuals, it ap-peared well worth investigating to as-certain if there are differences whichare sufficiently fundamental and ofsufficient magnitude to lend a reason-able probability to an identification ofa person from one or more of his hairs.In this series of papers it is hoped toreport studies of various observableand measurable differences of hair insufficient numbers that statistical anal-ysis may be employed to determine theexact variations of each of these fac-

tors which may be significant in deter-

mining individuality.

Early results of these studies appear

to point very definitely to the possibil-

ity of making such identifications with

a very considerable degree of proba-

bility. It has, for example, been cus-

tomary for some years to require all

students of criminological science in

the author's laboratory to identify a

single hair from one of twenty samples,

all of similar color and from individ-

uals of similar age. To the present, nosuch student who has completed theroutine examination has failed to re-port the identification correctly. Whilethis falls far short of placing a hair ona single member of the world's popu-lation, it must be remembered (a) thattwenty suspects in a single crime israther an exceptional number; (b)that the eliminative value of a failureto identify the hair as that of any ofthe suspect's is great; (c) that timeimposes on students a restriction onthe total number of hairs that can beexamined, and it is impossible as yetto say whether they. could equally wellpick, e.g. from 100 standards; (d) thatin any random group of suspects therewould be greater normal variationsthan are present in the selected groupof similar hairs used for this exercise;and (e) that the students in questionhave never before examined hairs andare in no sense experts in this exam-ination.

In addition to the question of locat-ing from which of a number of hairsamples a single hair has been taken,a considerable number of criminal

PAUL L. KIRK

cases involving human hair have beeninvestigated with results that are, tosay the least, gratifying. In one case,two fugitives from justice were locatedexclusively on the basis of a single haircontained in the hat of one of themwhich had been lost in flight. The iden-tification in this case was later con-firmed by fingerprints. In another case,hair believed to have come from thevictim of an assault was located in thelodgings of a suspect, while hair diag-nosed as that of the suspect was locatedon the victim. The diagnosis was con-firmed by a plea of guilty. In anothercase, the identification of the hair of asuspect was confirmed by sufficient ad-ditional evidence of other types that ajury found the suspect guilty. In theseas in other cases, the individualizationof the hair has without exception beenconfirmed when there were indepen-dent means of obtaining confirmation.It would be imprudent to concludethat the procedure may for this reasonbe made infallible, but the results cer-tainly justify further studies so that ashigh a degree of probability as possiblemay be attained in hair identification.At the very least, it is surely possibleto develop the technique to the pointof making it a valuable addition tocriminological methods.

Technique of ExaminationThe total possible number of factors

which might be studied in connectionwith human hair identification are verylarge. Only those which have so farproved to be of value will be briefly de-scribed here, though undoubtedly manymore will ultimately prove useful as

well. In order to make examinationsof hair, certain routine matters ofhandling and preparation must be con-sidered.

If the bodily origin is definitelyknown it must naturally be recorded,even to the extent of distinguishing be-tween crown, nape and sideburns ortemples of human head hair. Otherbody hairs need not be considered herefor they have not been studied to theextent of making individualization pos-sible as yet. Naturally it is necessaryto be able to distinguish body hairsfrom head hairs, a matter which isusually simple to the person who hashad some experience in hair examina-tion. It is as yet uncertain whetherhair from different portions of the headshows consistent differences which aresignificant, but the distinction of areasshould be made until evidence is ob-tained to settle the point.

The head hair is first examined with-out any cleaning or other treatment byplacing it on a microscope slide, cover-with a cover slip and examining it un-der magnification. At times there areparticles of adherent matter which maybe significant. Ordinarily the debris ismerely a mixture of dandruff, oil, andcommon dust. After determining theimportance of the debris, the hair iswashed thoroughly in a mixture ofequal parts of ether and alcohol in acovered dish. This washing should becontinued with agitation for about 15minutes, or even longer when prepar-ing it for the measurement of suchproperties as refractive index. In thelatter case it is sometimes necessary to

HUMAN HAIR STUDIES

make a second washing with clean sol-

vent to ensure absolute removal of allgrease. The hair is dried in the air,preferably on a clean filter paper, andthen it may be cut into lengths ofabout one half inch for convenience inmounting. Short hairs must be cut intostill shorter pieces for it is necessary tomake more than one mounting for a

complete examination. In measuringsome properties such as diameter, re-fractive index and birefringence, it isdesirable to make short sections notmore than 1 mm. in length. This is con-veniently done by mounting two razorblades on a thin brass block, so that theedges are parellel and about 1 mm.apart. This simple device will cut anynumber of short sections of equallength.

A portion of the hair is mounted dryunder a cover slip which is sealed tothe slide with a little Kronig cement(1 part beeswax melted with 4 parts

resin), taking care not to allow thecement to contact the hair. Anotherportion is mounted in Canada balsam.Millimeter sections are laid aside forspecial purposes, or else made as

needed. In case the amount of hair istoo small for simultaneous mountingsand without balsam, the dry mountmay be examined and later mounted inbalsam. In case of necessity, the bal-sam mount may be cleaned in xyleneand remounted dry.

Occasionally hair is encountered withsuch dense pigment that transmittedlight is inadequate for its examination.

In these cases the Ultropak illuminator

is helpful. If the magnification must be

great (e.g. 50x objective) it is some-

times difficult to find sufficiently thincover slips to allow the objective to belowered into focus. In this case a sim-ple expedient is to fasten the hair tothe slide by covering it with a piece oftransparent Scotch tape (16). Thistype of mounting may for conveniencebe substituted for all dry mounts ofhair. It has the disadvantage that ifthe hair is to be subsequently mountedin another way it must be recleaned toremove any adhesive from the tape.Air bubbles which are frequentlytrapped are another source of difficulty.

As a general rule it is unnecessary tomake cross sections, in spite of the verygreat prevalence of this custom. In dis-tinguishing species the cross section hasa very definite value which is, how-

ever, not so great even in this case asit has been considered by some. Inhuman hair studies, the only factorswhich are given by a cross section arethe minimum and maximum diameters,the appearance of the medullary canaland the cross sectional pigment distri-bution. The first factor is readily de-termined without sectioning (as will bedescribed later), and indeed, muchmore accurately, because of the tend-

ency of the hair to pull in cutting thesections, thereby giving an oblique cutrather than a normal 900 section. Thesecond factor is relatively insignificantin identification, and can also be seenin the longitudinal view, though some-what less clearly, with transmittedlight. The third factor occasionally hassignificance, chiefly in determining the

relative central or peripheral distribu-

tion of the pigment. This can be also

seen in the balsam mount by focussing

PAUL L. KIRK

up and down and observing the shiftin the maximum density of the pig-

ment. Finally, the technique of crosssectioning is not one that can be doneordinarily without considerable experi-

ence, and to a very considerable extent

it destroys evidence. For these reasons

it is considered preferable to save thecross section for a final resort in case

no decision can be reached without it.In the author's laboratory this has oc-

curred just once, and in that case moreexperience in the lateral examinationwould undoubtedly have settled the

point.

Necessary micoscropic observations

may now be made on the mounted hairsin any way desired. The use of magni-fications greater than about 50 0x is

generally useless. The increased thin-ness of the field and the poorerresolution with higher powers more

than offsets any advantage of greatermagnification. The single importantexception to this statement is the de-

tailed examination of the pigment gran-

ulation which must often be performedwith oil immersion objectives. As in-

dicated above, the use of the Ultropakilluminator is sometimes highly advan-tageous, particularly for examination

of the cuticle layer, but also for deeper

structure in many instances. For ex-

ample, the medullary canal is very

easily observed under this instrument.

Study of pigment distribution is gen-

erally made with transmitted light.

Characteristics for Study

Almost an unlimited number of char-

acteristics and sub-characteristics of

hair may be studied and at present it is

not only impossible to say how many

of these are subject to investigation

but also how significant any of them

may ultimately be found. Those which

have proved of value up to the present

will be listed here and discussed.

Morphological Factors

1) Color. This factor is the most

obvious one to the inexperienced indi-

vidual as well as to the expert. Its in-

terpretation, however, must be made

with caution. Certainly when gross dif-

ferences are found in the color of two

hairs, it is a fair assumption that they

did not have a common origin. This is

particularly true when the actual color

rather than the shade or hue is differ-

ent. But experience shows that differ-

ent hairs from the same head will fre-

quently have rather wide variations in

color, making necessary a careful scan-

ning of many hairs of the individual

furnishing the standard. This is espe-

cially true with blond hairs. Only if

the color of the questioned hair falls

within the known range of the standard

is this factor significant. If it falls

without, it is left to the investigator

to be sure that his standard is really

representative. Nevertheless, in a ma-

jority of cases the differences of color

may be legitimately used for prelim-

inary elimination.

It would be highly desirable to estab-

lish an absolute color chart for hair

(11) and in addition to make accurate

studies of the characteristics of hair

pigments in order that their chemical

identity or difference might be deter-

mined as a check on the color alone.

2) Diameter. Since human hair is

HUMAN HAIR STUDIES

nearly always oval in cross sectionrather than round, it is necessary that

the two extreme diameters be deter-

mined before any significance other

than a gross idea of the hair coarseness

may be attributed to the measurement.

An accurate cross section undoubtedly

allows the simplest measurements of

minimum and maximum diameters.

Since it is so difficult to obtain such sec-

tions, the technique employed in this

laboratory is to use millimeter sections

which have been cut as previously de-

scribed. These are placed on a slide

which has been slightly frosted by gently

rubbing two slides together with a little

fine, moist carborundum powder be-

tween them. Such a short section will in

nearly every case lie in its stable posi-

tion, i.e., with the broad diameter par-

allel to the surface of the slide. A cali-

brated ocular micrometer may then be

used directly to obtain the maximum

diameter, and a calibrated fine adjust-

ment on the microscope will give the

minimum diameter. For the latter

measurement the instrument is first

focussed sharply on the frosting of the

slide, and the fine adjustment microm-

eter is read; then it is focussed on the

very top of the hair section and read

again. With care this method gives re-

sults nearly as accurate as those read

from the cross section but with much

less effort, and avoids the important

posibility that the section is not cut

exactly across the hair.

The significance of diameter deter-

minations in individualization of hair

does not appear from preliminary ob-

servation to be very great. Certain in-

dividuals have relatively uniform diam-

eters throughout their hair while othersshow great variation. One case studiedshowed a three-fold difference in bothminimum and maximum diameters be-tween his smallest and his largesthairs. If sufficient hairs are available

for study, this variation itself shouldbe significant, i.e., a person with uni-

form diameters could be distinguishedfrom one of very non-uniform diam-

eters. Many data will need to be col-

lected before any absolute significancemay be ascribed to this factor. For thesame reasons, the index of curvature,small diameterlarge diameter is variable from hair tohair and from point to point on the

same hair, though it is probably truethat the average of a large number ofmeasurements, and possibly the range

of variation, may be shown to be sig-

nificant for individualization as well asfor racial characteristics.

3) Scale Count. By scale count ismeant the number of scales intersectinga line laid along the axis of the hair,

and of some known length. The usualtechnique in the author's laboratory isto move the hair so that one line of

the cross hair in the microscope ocularbisects the hair longitudinally while

the calibration marks of the ocular mi-crometer are at right angles to the

length of the hair. Each intersection of

a scale edge which crosses the bisectingcross hair is counted, usually over thelength of the ocular micrometer scale.

For comparative purposes the samemicrometer and microscope are used

with all the hairs in question so that no

absolute calibration need be applied. For

absolute data, the length of the mi-

PAUL L. KIRK

crometer scale is determined and thescale count corrected to that of somestandard length (e.g., 0.2 mm., as usedin this study).

The significance of scale count meansand ranges both appear to be very defi-nite. As eliminative factors each usu-ally serves to reduce the number ofpossible hairs by about 3/4 or 4/5, pro-vided enough counts are made so thatthe averages become reasonably sig-nificant. At least 25 counts are usuallymade before the average is taken, and

this average is only interpreted toabout +10%, though the average usu-ally falls closer than this to the grandaverage for the individual. More con-cretely, if the average scale count is 24,all hairs with averages below 22 andabove 26 would be considered as defi-nitely from another individual, andthose between 22 and 23 and between25 and 26 would be considered as im-probable, but subject to further com-parison. A final value for scale countaverage and range should be based onat least 100 counts, the averages beingmore closely interpretable. The statis-

tical significance and interpretation ofthese factors will follow in a subse-quent publication. We can concludehowever, that scale count has a veryconsiderable value both in descriptionof hair and as an eliminative factor.

4) Scale Picture. By scale pictureis meant the general characteristics ofthe scales which are observable, suchas the shape, regularity or irregularityof sizes, and edges, and such other fea-

tures as may be observed microscop-

ically. These characteristics are by far

the hardest to study or to discuss, in a

systematic fashion, but in spite of this,they may have considerable value inhair individualization. It is observedthat many hairs have regular scalestructure with little variation from partto part. When this is the case, pre-liminary studies indicate that it is acharacteristic of the individual andmay be expected on all of his headhairs to a great degree. On the otherhand, when the scales are irregular insize (e.g., large interspersed withsmall), in shape, or in contour lines,serations, etc., that also will be foundquite generally over the range of hairsfrom that individual. Except for the

work of Eddy (8), little if any sys-tematic study has been made of thesescale properties, but it seems a subjectwell worth investigating, even thoughnothing more definite may be said thanthat the experienced hair examiner willbe able to use the scale picture to avery considerable degree in individual-izing hair. From a limited number ofhairs of different origin, it has beenfound possible in many cases to identifyunknown hairs correctly on the basisof this property alone.

(5) Pigment Distribution. Of thevarious factors utilized in individuali-zation of human head hairs, the distri-bution and appearance of the pigmentgranules in the cortex of the hair has

proved to be one of the best, if not thevery best. Again, so many factors areincluded under the term of pigmentdistribution that it is difficult to discussor adequately separate them. First

might be considered pigment density

and density distribution. In general the

pigment density is inversely propor-

HUMAN HAIR STUDIES

tional to the amount of light that may

be transmitted through the hair undersome standardized set of conditions.

Where the density approaches a maxi-mum, there is almost no light trans-

mitted as in certain very black hairsfound most often in the negro race and

to a lesser extent in races of Asiatic ori-

gin. A minimum density would be

found in very light blond or gray hair.The density distribution refers to thefact that in most cases the pigmentgranules in human hair tend to cluster

close to the periphery of the hair, butthis tendency varies somewhat fromperson to person. It may be observed

in cross section most easily, but mayalso be studied by focussing up anddown on a balsam mount of a sectionof the hair lying lengthwise of the slide.

Another sub-factor of importance isthe distribution with respect to size ofgranules. Some persons show a relativeuniformity of size which may rangefrom so small as to be scarcely visibleunder high power, up to granules whichare very coarse. Most persons exhibita greater or lesser lack of uniformityof granule sizes, so that in one hair wemay see all sizes of granules. However,the relative proportion of coarse to finegranules (based on some arbitrary sizebasis) will vary enormously betweenindividuals, but not greatly betweenhairs from the same individual. Thisis a difficult factor to treat quantita-tively though it is quite apparent to theexperienced observer.

Another factor which is importantand even less susceptible to exact de-scription is the shape of the pigment

granules. Unquestionably the pigment

granulation varies greatly between in-dividuals with respect to the general

shape of the granules which are laiddown. Normally the granule is defi-

nitely elongated, so much so in some

cases as to appear as a thin streak. Inother cases the granules approach a

roughly oval shape with a much lesser

degree of elongation, while still other

individuals show a definite alignmentof discrete granules, giving the appear-

ance of great elongation. A study ofthis factor will show quite characteris-tic differences between the hair of dif-

ferent people, particularly with respectto the coarser granules, and becomingmore significant as the different sizedgranules are considered.

Pigment distribution, consisting as itdoes of these various factors may beutilized to a very great extent in hairindividualization. Because of its com-plex nature, however, it is a factorwhich must be very thoroughly studiedover a considerable period of time be-fore it will yield its maximum results.It is hoped that it may be broken downinto its sub-factors for study and thatreproducible means may be found forevaluating each of the sub-factors.

(6) Medullation. The presence orabsence of medulla in head hair haslittle significance, nor does its appear-ance have much more. It is true thafindividuals vary considerably with re-spect to the total medullation shownby their hair, and to this extent thefactor becomes useful. Cases have beenobserved in which nearly every hairshowed medulla and most hairs had

PAUL L. KIRK

virtually continuous medulla. The moststriking case in which this was found

was with an elderly woman whose cor-

tex was uniformly devoid of pigment.

Physical Factors

Refractive Index. As will be shownin a later paper, refractive index ofhair is a characteristic of very definitevalue, both for individualization and

for race and sex determination. Therange of refractive index is consistently

higher for female than for male hair,

and apparently for Asiatic races thanfor European races. Within the same

sex and racial type, the range is fairlynarrow, but broad enough to cover sev-

eral times the probable error, and

therefore, to serve for the elimination

of at least 3/4 of all possibilities. As anindividualization characteristic, it iscomparable in its eliminative and posi-

tive value to scale count.

Birefringence. All hairs show the

characteristic of being more or less re-fractive, though with the exception ofhairs used as textile fibers, little notice

of this fact seems to have been recorded.

Unlike a truly crystalline material, thelack of morphological homogeneity inthe hair makes quantitative study of

this property exceptionally difficult andit has not progressed to the point atwhich any final conclusions may bedrawn. Preliminary investigation ap-pears to indicate that this factor, too,will have a definite eliminative andsome positive value for individualiza-tion when the means of studying ithave been sufficiently standardized and

defined. When two hairs of the same

diameter are examined between crossedNicol prisms, it will be observed that

those from different sources frequently

show different interference colors,

while those from the same origin willgenerally be of the same color. Further

careful study of this property is ex-pected to produce results of very con-siderable significance in individualiza-

tion of human head hairs.

Miscellaneous. Many additional phys-

ical properties suggest themselves.

Drawing analogies to the extensivework done with the mechanical proper-

ties of wool, such factors as tensilestrength may be of consequence. It

has been noted that permanently wavedhair stretches very readily in compari-

son with untreated hair. This suggests

the development of a method for studyof the stretch coefficient, a matter

which is receiving preliminary investi-

gation. Virtually nothing is now known

of the electrical properties of hair

which may also prove to be of definitesignificance when they are studied.

Chemical Factors

It seems virtually certain that thehair will reflect differences in its chem-

ical environment during growth. Again

making use of the analogy with woolit is recognized that the cystine contentvaries with the nutritional state of thesheep. It is equally certain that someelements such as arsenic and probablysilicon are selectively taken up in thehair. Though there is little availableproof, it is obvious that hair color itself

HUMAN HAIR STUDIES

must to some extent depend on chem-ical differences of the pigment, and itis equally logical to believe that atleast a part of the morphological differ-ences in hair are based on correspond-

ig chemical differences. As previouslymentioned, the rate of solution of thehair bulb in caustic potash is widelyused for indicating sex of hair, and theextensive work of Tadokoro (17) andothers (18) indicates that sex has avery important effect on the chemicalmakeup of epidermal structures, in-cluding hair. The difference in hair

distribution in the sexes, as well asother similar secondary sex character-istics may be largely a reflection of thedifference in the basic chemical make-up of the system exhibiting these prop-erties.

All of these factors, and others,

clearly point to a large undevelopedfield for investigation in the basic chem-istry and chemical differences of hair.So far as is known to the author, no

chemical methods have been employedthus far in hair individualization.

Other Factors

Many factors of an artificial, patho-logical or accidental nature may enterin the individualization of human hair.Most common of these are self imposedtreatments such as artificial waving anddyeing. While such treatments are usu-ally very obvious to the examiner andwill have a greater or less significance

in the individualization, the most im-portant result is probably the altera-

tions that they produce in the othermore basic factors listed for study.

Permanent waving, for instance, alters

many morphological factors including

diameter and scale count, and physical

properties such as birefringence and

tensile strength. Dyeing naturally al-

ters hair color, but not pigment color,

while bleaching alters the latter as

well.

Various diseases affect the growth or

permanence of the hair. To what ex-

tent such alterations as are produced

by disease may be expected to alter

the morphological, chemical or phys-ical properties has not been estab-

lished, but it is scarcely to be doubted

that there are such effects. While acomplete study of hair must take into

account all such factors as the above,their criminological importance is prob-ably not great except in instances in-volving a long lapse of time betweentime of collection of questioned hairand of standard.

The large number of morphological,physical and chemical factors whichmay be studied in hair investigation,

and the preliminary indication from astudy of a few of these factors definitelypoints to the possibility that human

head hair may be positively individ-ualized and used in personal identifica-tion. Before such identification can beconsidered as definite, large numbersof data must be collected and analysedstatistically.

(List of References on next page.)

PAUL L. KIRK

REFERENCES

1. Smith, S., Forensic Medicine (1936) Lon-don.

2. Glaister, J., and Glaister, J. Jr., A Text-book of Medical Jurisprudence and Toxi-cology (1931) Edinburgh.

3. Hausman, L., "The Relationships of theMicroscopic Structural Characters of Hu-man Head Hair," Amer. J. Phys. Anthro-pol., 8: 173 (1925); "Structural Character-istics of the Hair of Mammals," Amer.Naturalist, 54: 496 (1920); "A ComparativeRacial Study of the Structural Elements ofHuman Head Hair," Amer. Naturalist, 59:529 (1925); "The Pigmentation of HumanHead Hair," Amer. Naturalist, 61: 545(1927); "The Cortical Fusi of MammalianHair Shafts," Amer. Naturalist, 66: 461(1932).

4. May, L. S. Crime's Nemesis (1936) NewYork.

5. Trotter, M., "The Forms, Size and Colorof Head Hair in American Whites," Amer.J. Phys. Anthropol., 14: 433 (1930).

6. Trotter, M., "A Review of the Classifica-tions of Hair," Amer. J. Phys. Anthropol.,24: 105 (1938).

7. Eddy, M. W., "Hair Classification," Proc.Pennsylvania Acad. Sci., 12: 19 (1938).

8. Roig, J. D., "Technique for the Medico-legalExamination of Hairs," Ann. med. legalepolice sci. criminol., 12: 225 (1932).

9. Harvey, L., "The Examination of Hairs,"Police J., 11: 61 (1938).

10. Fiala, G. F., "Preparation of Hair forCross-Section Examination," Amer. J. Phys.Anthropol., 14: 75 (1930).

11. Bellamy, R., "Measuring Hair Color," Amer.J. Phys. Anthropol., 14: 75 (1930).

12. Smith, S., and Glaister, J., Recent Advancesin Forensic Medicine (1931) London.

13. S~derman, H., and O'Connell, J. J., ModernCriminal Investigation (1936) New York.

14. Danforth, C. H., Hair with Special Refer-ence to Hypertrichosis (1925) Chicago.

15. Lambert, M., and Balthazard, V., Le poilde l'homme et des animauvx (1910) Paris.

16. Herzog, A., "A Simple Method for PartlyMounting Fibers for Microscopic Examina-tion," Melliand Textilber., 19: 405 (1938).

17. Tadokoro, T., Sex Differences from theStandpoint of Biochemistry.

18. Piepenborn, J., "Chemical Differences inMale and Female Hair," Z. ges. exptl.Med., 76: 587 (1931).

[The second paper of this series (II. Scale Counts) will appear in the next issueof this Journal.]