OR, A TREATISE ON PILE. 91 



which (hair) was of a bright blue color, owing to its having taken up some of the coloring 

 matter used in the tattooing. We have repeatedly tried to inject a hair, but have never 

 succeeded. Again, a woman, about thirty, became enciente, and at the seventh month, 

 her skin of the face first assumed the color of oxide of iron ; and afterwards it became 

 black. On some days it was of a deeper shade than on others ; her hair was naturally black, 

 but it assumed a darker shade. The black of her face disappeared two days after her 

 accouchement. Besides, Keidline mentions a case where the hair became bright yellow 

 during a fit of jaundice ; but he does not mention the original color, and Alibert tells of a 

 blonde-haired woman whose hair became black after a severe accouchement. (See Diet, des 

 Sci. Med., v. 43, p. 273.) A still more extraordinary case is mentioned in p 503, of the 

 same work, of a female whose hair, shortly before her death by consumption, changing 

 from white to black.* The hair which is rubbed from the hides of horses with colored 

 pile, sometimes is succeeded by white hairs, and sometimes, (though less frequently,) by 

 hair of the original color. 



When a wound heals " by the first intention," the original skin closing and joining, 

 hair grows and continues of the same color it was originally; but when it heals "by 

 granulation," a new and imperfect skin is formed, with a very white hue and smooth surface, 

 and upon this no hair will grow. Feeding an animal for some time upon madder turns the bones 

 red, but it has no effect upon the hair. Dr. Belchier, an English physician, from seeing a pig 

 which had been fed at a dyeing establishment have reddish colored bones, first discovered 

 the phenomenon. He repeated the experiment upon other animals, and always with the 



same result, 



i 



OF THE POLARIZATION OF LIGHT BY PILE. Hairs polarize light. (Mandl, Traite. Prac. 

 du Microscope, p. 165.) Common light originates in vibratory motions in every direction 

 transverse to the ray ; but polarized light is caused by vibrations, transverse to the ray, 

 and in one direction only. The part of the hair which is instrumental in producing this 

 phenomenon is, probably, the cortex, which is scaly. Polarization may be caused by 

 reflection, refraction or double refraction, f 



In viewing hairs under the microscope, we must remember the shape of the hair, for 

 light impinging on its surface, being reflected according to the angle of incidence, will be 

 reflected differently as the hair is cylindrical, oval or flat. We should also recollect that 

 the rays of light which emanate from the reflector of the microscope, situated beyond or 

 beneath the hair, being of diiferent lengths, will cause a series of light and dark colored 

 stripes and shadows, which, unless properly understood, will cause false impressions of 

 the object. 



And, lastly, the rays of light, striking directly upon the hair, and those reflected by the 

 reflector, which is beyond or below the object, may interfere and nullify each other. This 

 danger is increased when two reflectors, one above and one below the object, are used. 



* May this not have been a falling out of the old colorless hair, and its place being supplied by new black ones? 

 t The shadow lines of light upon hairs, which, owing to their minuteness, are invisible to the naked eye, become colored 

 under the microscope, 



23 



