We may, however, meet with straight hair (not smooth), or curly hair (not kinky). In addition to these forms, which among us represent the extremes, there are also two other forms—namely, wavy hair (in ample curves) and spiral hair (forming much narrower curves, the so-called ringlets). Corresponding to these various qualities of hair, there are essential differences in the physical structure of the stem or shaft of the hair itself. If we make transverse sections of hair and examine them under the microscope, we find that the resulting geometrical figures are not all equal: the forms of the sections oscillate between rounded and ellipsoidal forms. Furthermore, there are races in which we may find hair having a circular section (smooth hair) and there are others in which we may find, on the contrary, an extremely elongated elliptical section (kinky hair); in the first case the hair is a long, bristly cylinder; in the second, it is a ribbon with a tendency to roll up.
Fig. 130.
In general, the straighter the hair is, the nearer its cross-section approaches a perfect circle; and the more curly it is, the nearer its cross-section approaches an elongated ellipse. The accompanying examples are drawn from the results of my own study of the women of Latium; they represent five microscopic preparations. The figure in the middle (No. 3) represents straight hair; the two figures, No. 1 and 5, are from curly hair; No. 2 is wavy hair, and No. 4, close-curled hair, or ringlets. Thus we see how widely the sections of hair differ according to the relative degree of curliness; and conversely, how identical the two sections, Nos. 1 and 5 are, both of them taken from equally curly hair, although from different heads. Straight hair has an almost circular section, although, slightly elliptical; this proves that really straight hair does not exist; in fact, even when it attains the maximum degree of smoothness, it retains a tendency to curl, which is shown, if in no other way, by the readiness with which it acquires a waviness, if habitually kept braided. There is no other section so perfectly circular as that of the red races, thus demonstrating the bristle-like rigidity of the smooth type of hair. Wavy hair is that which, in the form of its section, approaches most nearly to straight hair; it is a slightly elongated ellipse (No. 2).
Anomalies relating to the Pigment, the Skin and the Piliferous Appendages: Pigment and Skin.—There are certain congenital anomalies of the skin, occasionally to be met with, among which I make note of the following principal ones:
a. Anomalies due to Hypertrophy of the Pigment and the Corium: Ichthyosis.—The surface of the skin presents large, raised, irregular patches of various dark colours tending to maroon.
b. Anomalies due to Hypertrophy of the Pigment:
- Nævi Materni: dark isolated spots (moles, birth-marks).
- Freckles: small, light brown spots, no larger than the head of a pin, scattered over the body, principally on the chest and face.
- Melanosis: the entire skin has a dark appearance, similar to that of the lower races of mankind, but especially on the face and hands.
c. Anomalies due to Atrophy of the Pigment. Albinism.—The skin presents an appearance of milky whiteness; even the hair is white, and the iris of the eye is red.
Wrinkles.—The wrinkles of the face are deserving of attention, as being a detail of noteworthy importance. In regard to wrinkles, two points should be noted; a. precocity; b. anomalies.