牛放线菌 (Actinomyces bovis)，革兰氏染色涂片，奶牛

Photomicrograph of a fine-needle aspirate from a mandibular mass in a cow with actinomycosis. Actinomyces bovis cells appear as characteristically branching, slender, gram-positive rods. Gram stain; original magnification, 1000X.