Figure 1. Trajectory of rib 10 during the application of external forces to the rib.

The data points were obtained in a representative animal while the animal was made apnoeic by mechanical hyperventilation and the 10th rib pair was pulled in the lateral (open circles) and the cranial–dorsal direction (filled circles). The lines of best fit to the data are also shown. The lines did not pass through the origin, and the small positive intercepts with the ordinate were considered to be artifacts.