The neurotic theory of the origin of alopecia areata is still held by many der matologists.
Prolonged exposure to the vacuum tube of an x-ray apparatus may give rise to localized falling of hair.
Case of dermatitis and alopecia after the use of the Roentgen rays in a young man, aged 17, in whom experiments were carried out during four weeks, once or twice each day. The dermatitis re sembled that caused by burns. An improvement soon occurred. Marcuse (Deutsche med. Woch., July 23, '96).
Case of alopecia areata as a result of exposure to the Roentgen rays during forty minutes, using a Thompson double focus or standard vacuum-tube. The dis tance between the tube and skull was a little over eighteen inches. A large area of hair missing upon that side of the head exposed to the vacuum-tube; no premonitory symptoms of itching or in flammation; the hair had suddenly fallen out three weeks after the exposure.
The integument appeared bald and somewhat elevated, and slightly oedem atous; no redness; sensibility not im paired; no scaling. Under stimulating and hygienic treatment downy hairs are beginning to show themselves. F. S. Kolle (Buffalo Med. and Surg. Jour., Dec., '96).
True alopecia areata seems to occur in syphilitic subjects more frequently than in other persons.
Areas of absolute alopecia which occur in the scalp or beard in syphilis may be small and few, well circumscribed, last ing a short time, but recurring often. This is very different from that general thinning of the hair seen early in the disease, which never returns. A Fournier (Jour. des Praticiens, Jan. 19, 1901).
The percentage of alopecia areata in various countries is approximately as follows: France, 3 per cent.; England, 2; Scotland, 1.5; Vienna, 0.75; North Germany, 0.75 to 1; America, 0.5.
(Crocker.) In Lille, of 5000 cases of skin disease, 149 eases were alopecia areata; in Lyons, of 2765 cases, 17; in Vienna, of 5000, 40; in Berlin, of 1050, 9; and in another serics of 3008 cases, 30 were alopecia areata. In America, as shown by the statistics of the American Dermatological Association, alopecia areata was found in 794 eases out of 123,746 cases. E.
Besnier ("Sur la Pelade," Travail lu 5. l'Aead. de Mod., July 31, 'SS).
Pathology. — The initial stage alone of ordinary benign alopecia areata is microbic. As soon as the patch be comes smooth, microbes can no longer be found, neither in the skin nor in the follicle. In the beginning of the disease almost all the follicles are infected with. innumerable microbian colonies belong ing to a single bacillary species always the same.
In benign cases the follicular infec- tion is transitory; in chronic or total alopecias the same microbe is found constantly, with the same localizations.
The invariable presence of this microbe wherever there is a beginning lesion gives it a value other than that of an ordinary secondary infection. However, this mi crobacillus, notwithstanding certain dif ferences of form, cannot be distinguished with absolute certainty from the microbe which Hodara has described as the bacil lus of acne. If the bacillus of Hodara and that of alopecia areata are the same, we must ascertain why in every case of alopecia this secondary infection is con stant, and what role it plays. If they are different, they must be differentiated ex perimentally. Finally, they may be the same bacilli which, under different vital conditions, may or may not secrete a toxin capable of producing alopecia. (Brocq.) According to Sabouraud, alopecia and alopecia areata are practically identical. The patch of alopecia areata is only an attack of acute circinated seborrhoea: in other words, the bald only become bald by a diffused process of chronic alopecia areata. Alopecia areata is a contagious disease, the extension of which is marked by the appearance of a special form of hair: the club-shaped hair. This hair appears with the disease, disappears at the same time that it ceases to extend, and reappears with the renewal of ac tivity. Where the malady is active it is never wanting.