McGeown JG, McHale NG, Thornbury KD.
The role of external compression and movement in lymph propulsion in the sheep
hind limb.
J Physiol 1987 Jun;387:83-93

1. Pressure fluctuations and lymph flow were measured in metatarsal lymphatics in
anaesthetized sheep. 2. Intermittent compression significantly increased lymph
flow when this was applied over the hoof but did not increase flow significantly
when applied over the metatarsal region. 3. In a second preparation a 15 cm
length of metatarsal lymphatic was cannulated at both ends and measurements were
made of the ability of the duct to pump saline from an inflow reservoir through
an outflow at the same height. 4. In the absence of external forces fluid was
propelled by the lymphatic's intrinsic contractions but when intermittent
compression was applied over the metatarsal region flow increased almost
fourfold. 5. When animals with the doubly cannulated duct were allowed to
recover, the effect of normal limb movements on fluid propulsion was examined.
Under these conditions flow only occurred in response to intrinsic lymphatic
contractions and appeared to be unaffected by the animal moving round the cage.
6. These results suggest that the effects of external forces on lymph flow are
more dependent on compression of tissues in the lymphatic drainage area than on
compression of the main lymphatic ducts. External compression can increase fluid
propulsion by these vessels but, since forces of adequate magnitude appear not to
be encountered in normal hind-limb movements, lymph propulsion in this region
must depend on intrinsic lymphatic pumping.