Mallein must be used under precautions like tuberculin. It must be obtained freshly prepared from a reputable maker. If preserved for months its force may be largely lost. The animal to be tested should be in his customary environment, and not just arrived from a railroad journey nor other cause of excitement. He must not be fevered as any rise of temperature is then equivocal, and a fall of temperature, which sometimes occurs in the febrile system under mallein, is no sure evidence of glanders. Reaction sometimes fails in advanced cases of glanders, but in such a case other symptoms are usually diagnostic so that mallein is superfluous and should not be misleading. The greatest care should be taken to prevent infection from the syringe, nozzle, skin, hands, etc., as other infections may give rise to local swelling and hyperthermia (see tuberculin test). If a first test leaves the matter in doubt, the animal should be secluded and tested again in a month (some prefer 3 months). _Pathological Anatomy._ The colonization of the bacillus mallei in a tissue usually determines a concentration and multiplication of leucocytes, so as to form rounded nests of small lymphoid cells in a scanty fibrous network. These may be miliary or by aggregation they form masses the size of a pea or larger, which bear a close resemblance to the neoplasms of tuberculosis. As in tubercle the central cells of the group, degenerate, forming a granular fatty debris, and constituting an ulcer or abscess. In certain cases with a proliferation of fibrous tissue a cicatricial material is developed. Another characteristic lesion is the occurrence of hyperplasia in the walls of the lymph vessels so as to constitute firm tender cords, and the infiltration of the adjacent lymphatic plexus.