MEDICOLEGAL EXAMINATION OF HAIRS.

A NUMBER of questions present themselves in connection with the medicolegal examinations of hairs, among the most important of which are the following:

1. Is the material examined hair or some other fiber?

2. If hair, from what animal did it come?

3. If the hair is human, can it be identified as the product of a given individual?

4. If of human origin, from what part of the body did the hair come?

5. What was the age of the person from whom the hairs were derived?

6. How were the hairs removed from the body?

The first question is usually easily answered. It is true that to the naked eye various articles, chiefly vegetable fibers, may simulate hairs; but by the aid of the microscope all other bodies may be distinguished from them.

The distinctive features of hairs that are recognized by even low powers-200 to 300 diameters-are: 1. The shingled or terraced (" imbricated") surface. 2. The distinction between cortex and medulla. 3. The pigment-granules in the cortex. 4. The cells composing the medulla. 5. The transition in structure from shaft to root, and the peculiar sheath of the latter.

It is seldom that all these features are found in a single specimen submitted in a judicial inquiry; but, fortunately, positive identification can be made through the detection of several of them.

If needed, confirmation of the identity can be secured by submitting the supposed hair to certain chemical reagents; a strong mineral acid, heated, causes the disintegration of a hair into the component cells.

The bodies from which hairs must, by these features, be distinguished are cotton, linen, silk, wool, and vegetable fibers (Plate 13). Cotton is a flat, tape-like fiber with a tendency toward a spiral twist; linen is a jointed, bamboo-like fiber with transverse markings at irregular distances; silk is a cylindric fiber without markings, but strongly refractive. Wool, as a variety of hair, presents the imbricated surface characteristic of hairs: while in general cylindric, its diameter varies in different parts. Any of these fibers may, of course, present the colors imparted by the dyes used in the cloth.

The second question is from what animal the hairs have been separated. Fortunately, the query does not usually include the whole cata

logue of hairy animals; else the solution of the problem might become practically impossible, because of the great similarity between individual hairs of different species. Practically the only animals requiring consideration are those which, living or dead, enter into human environment-the domesticated quadrupeds, the parasitic rodents, the animals whose skins are converted into clothing. The hairs of these represent different types, and can all be distinguished positively from human hair (Plates 13, 14).

The third question often presented to the microscopist in a legal inquiry is whether hairs admittedly human can be identified as the product of a given individual; whether they must have grown on the body of a certain person, and could not have been furnished by any other.

This question must be answered always and distinctly in the negative. While similarity in color and size with that of a given individual may be marked, there is nothing peculiarly characteristic in the hairs of one person to distinguish them from the hairs of many others of similar complexion. It may occasionally happen-as in one case examined by the writer-that the hairs in question present certain peculiarities of structure due to disease; the detection of similar abnormalities in hairs from the suspected source would naturally furnish a probability, but not a certainty, of a common origin. Aside from these necessarily rare cases, identification of the individual from whom given hairs are derived is dependent upon community of size, length, and color; and these are insufficient to warrant more than a probable conclusion.

A fourth question is, From what part of the human body are the hairs under examination derived? This question may often be answered definitely because of the following facts :

1. The long, soft hairs from the scalp and beard are distinguished both by their length and by their gradual tapering from root to point.

2. The short, thick, stiff hairs from the eyelashes and the eyebrows, while averaging almost the same thickness as scalp hairs at the root, taper rapidly toward the point.

3. The short, slender, flexible hairs from the general surface of the body-the so-called lanugo or down-have, on the average, a much smaller diameter than other hairs, even than the equally short but thick hairs from the eyelashes. These downy hairs, moreover, frequently exhibit no pigment-granules in the cortex; and the medullary canal is apt to be relatively small and is frequently absent.

The average diameters of hairs from different parts of the body may be approximately stated as follows:

350

1

Scalp hairs, inch in the male, inch in the female; the variations in different persons may, however, be extreme-from 1 to zu inch, for example.

150

Hairs from the beard and mustache are usually the thickest of the body, ranging from to inch; they usually exhibit the greatest diameter on the chin and upper lip, shading off in diameter as they approach the scalp above and the neck below.

1

3

O

6

7

1, Sheep's wool (X 200). 2, Linen fibers (X 200). 3, Cotton fibers (X 200). 4, Hair from human head (200). 5, Transverse sections of hairs from human head (x 200). 6, Hair from human beard (X 200). 7, Hairs from back of hand (x 200).

Hairs from the eyebrows, lids, axillæ, and pubic region present about. the same diameter at their roots as do those of the scalp; though here again great variations are found in different individuals.

The downy hairs from the general body surface are notably less in diameter than those in the so-called hairy parts of the body; they average from 0 to 1 inch in diameter near the root.

1

1

A fifth question sometimes propounded to the expert microscopist is, What was the age of the person from whom the hairs were derived? Here again his answer is restricted by serious limitations, and must be based upon the application, to the question at issue, of the following facts:

The downy hairs of the fetus and of the new-born infant contain no pigment and no medullary canal.

The hairs of children before puberty frequently have no medullary canal; they are relatively slender when compared with hairs of the same length and locality from adults.

A sixth query to which an answer may be sought through the microscope is, Were the hairs forcibly pulled out, shed from natural causes, or cut off?

This question can be answered, as a rule, decisively on the following facts: The root of a growing hair is concave, fitting over the convex papilla from which it grows. When forcibly separated from the head, the root end shows this concavity, as a rule; a bunch of hairs, most of which exhibit this feature, may with certainty be affirmed to have been forcibly pulled from the body. On the other hand, hairs which have fallen from natural causes exhibit little or no concavity at the root end.

A hair which has been cut from the head or other part naturally shows a plane surface, or something approximating this, where the cutting instrument severed the hair. The cut surface is sometimes uneven, because the different fibers composing the shaft have been severed at various levels.

The hairs growing upon the human body may be considered in three categories:

1. The long, soft hairs from the head.

2. The short, stiff, thick hairs from the eyelashes.

3. The short, slender, flexible hairs from the general surface of body and face-the so-called lanugo or down.

The long hairs from scalp and beard are naturally the most frequent subjects of microscopic examination for judicial purposes; in rarer cases the downy hairs, overlooked perhaps by naked-eye examination, have been magnified by the microscope into formidable witnesses of guilt. In one case in which the writer was engaged the presence of these diminutive hairs in blood-stains on a knife strongly confirmed the inference, from measurements of the blood-corpuscles, that the blood was of human origin.

In all cases where the identity of hairs is to be determined it is extremely desirable that several hairs be obtained for examination ; because some of the structural peculiarities upon which the recognition