A laboratory exercise in somesthesis that is expeditious, inexpensive, and suitable for large classes.

A teaching laboratory is described that demonstrates two principles of the somatosensory system: 1) the "spot-like" nature of skin sensitivity and 2) tactile acuity. This laboratory has been used for a large medical school class (140-160 students). One reason for the success of this laboratory is the ability to provide a sufficient number of stimulating apparatuses. The two-point discrimination device used to measure tactile acuity can be made easily and cheaply. In addition, two other demonstrations are described that are suitable for smaller classes or that students can do on their own. Although this lab was designed for medical students, the content makes it suitable for undergraduate or high school students.