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Rh believed to occur also in the Alaska territory. It is found principally in valleys and near the foot-hills of mountains in sharply-defined and limited areas, and is confined to the spring months, the greatest number of cases occurring between March and July. It attacks any age, either sex, and is not directly contagious.

Symptoms.—A short period of malaise is followed by chills, which are repeated with diminishing

Fig. 64.—Dermacentor venustus, ♂. (By courtesy of Prof. Nuttall.)

severity at irregular intervals throughout the attack. By the second day the temperature has risen to 103° or 104° F., and by the fifth day to 105° or 107°. A typhoid-like condition, with low muttering delirium and semi-consciousness, is rapidly developed. If the patient is to recover, the temperature begins to fall about the end of the second week, fever subsiding usually by lysis.

About from the fourth to the seventh day an