(_a_) The hair has changed in color in many cases. Of twenty-seven patients suffering from neuralgia of the ophthalmic division of the fifth, eleven had more or less decided localized grayness of hair on that side. The amount of this varied greatly, from mere patches of gray near the roots of the hair to decided grayness of the majority of the hairs over the larger part of half the head, nearly to the vertex; but in each case it was a change of color that did not exist on the other side of the head. In four of these cases there was also grayness of part of the eyebrow on the affected side. A very remarkable phenomenon, which I have sometimes identified, is fluctuation of the color, the grayness notably increasing during, and for some time after, an acute attack of pain, and the same hairs returning afterward more or less to their original color. My attention was first called to this curious occurrence in my own case. I have so often related this case [see, for instance, my article on Neuralgia in "Reynolds's System of Medicine," vol. ii.] that I shall merely recall the fact that, when pain attacks me severely, the hair of the eyebrow on the affected side displays a very distinct patch of gray (on some occasions it has been quite white) opposite the tissue of the supra-orbital nerve, and that the same hairs (which can be easily identified) return almost to the natural color when I am free from neuralgia. I must, however, add the very curious fact, which I observed accidentally in experimenting (as regards urinary elimination) on the effects of large doses of alcohol, that a dose sufficiently large to produce uncomfortably narcotic effects invariably caused the same temporary change of color in the hair of the same eyebrow, even when no decided pain was produced, but only general malaise. The subject will be again referred to under the heading of Pathology.