The compounds shown by the structural formulas below have analgesic effect and are used in compositions and methods for treating mammal in need of such treatment. The system provides guidance, e. A predetermined region of the diffuser sheet facing a region of the polarizer, where an hourglass phenomenon occurs, is formed to permit a smaller quantity of light to be transmitted therethrough than other regions of the diffuser sheet. The measurement system has a second sensor configured to measure light passing through the sample media.