Fig. 5. Pressure changes (Pa) that develop in the brachial lymphatic sac during expiration in C. marinus and L. catesbeiana (means ± s.e.m.) compared with the estimated range of 0.5–1.0 cm (50–100 Pa; shaded box) of gravitational pressure necessary to raise lymph to the subvertebral lymph sac. Values were not different between the two species (P>0.05).