Fig. 6. Stylized models of C. marinus illustrating the hypothesis for the effects of lung ventilation on vertical lymph movement. (A) Lung deflation causes an increase in subvertebral lymph sac volume and a decrease in pressure, resulting in movement of lymph from the brachial lymph sac. Posterior skeletal muscles are also active during expiration, providing movement of lymph vertically in the posterior portion of the animal. Red arrows indicate the direction of lymph movement. (B) Lung inflation increases the pressure within the subvertebral, dorsal and lateral lymph sacs and forces lymph towards the anterior (Ant. LH) and posterior (Post. LH) lymph hearts. Red arrows indicate the direction of lymph movement.