relapse; that in many instances it has definite premonitory symptoms; that it has peculiar lesions; and that it tends to terminate by crisis; in other words, that it behaves like pneumonia or any other specific fever—Sambon has boldly asserted that siriasis is a germ disease, like yellow fever or dengue, and, like these, is caused by some organism which demands for its development a high atmospheric temperature and certain, as yet unknown, local conditions. Time will show how far this hypothesis is correct. In my opinion it has more in its favour than any of the many theories that have been based on a purely thermic etiology.
Symptoms.—Though sometimes coming on suddenly during exposure to the sun, siriasis is very often preceded by a distinct prodromal stage. It is frequently developed independently of any direct exposure to the sun; not seldom the attack comes on during the night.
Among prodromata which may show themselves with greater or less distinctness for an hour or two or even for a day or two before the full development of the attack, may be mentioned great disinclination for exertion, pains in the limbs, drowsiness, vertigo, headache, mental confusion, sighing, anorexia, thirst, intolerance of light—sometimes accompanied by chromatic aberrations of vision, suffused eyes, nausea and perhaps vomiting, prsecordial anxiety, sometimes a sense of impending calamity, an hysterical tendency to weep, a very hot dry skin, and a quickened pulse. Longmore called attention to excessive irritability of the bladder as a common prodromal symptom. This is a valuable and easily recognized danger-signal when present, and one the significance of which has been confirmed and emphasized by subsequent writers; it is possible, however, that its frequency has been exaggerated.
Though generally present in greater or less degree, and for a longer or shorter time, in many instances these prodromal symptoms are not remarked, the first indication of anything wrong being perhaps a short stage of restlessness, or possibly of wild
