An apparatus and method for treating viral infections delivers electrical stimulation to the skin or mucosa of a patient. Each weak discriminator calculates a feature amount to be used in a calculation of an evaluation value of the image data, and discriminates whether or not the object is included in the image data by using the evaluation value. To maintain engine speed in spite of adjustments to the engine spark, the engine air mass is also adjusted. The screen panel receives projection light projected from behind for image display, and thereby displays an image thereon. The limb piece has a closed ring, or a slotted ring as stated above.