1 Collection of skin lymph separately from muscle lymph has enabled us to repeat earlier experiments in which lymph was collected from the whole hind limb to determine whether the changes then observed were the result of changes occurring in the skin or the muscle or both.2 After thermal and chemical injury, it appeared that most of the changes were due to leakage of enzymes from the muscle; after freezing, changes occurred in both skin and muscle lymph while ischaemia caused no significant changes in either skin or muscle lymph.3 After mild thermal injury it took longer for the enzyme leakage to reach a maximum in muscle lymph than in skin lymph. It seems likely that the changes were buffered by the large tissue space of muscle.4 Lactic dehydrogenase (LDH) activity appears to diffuse from muscle into skin since although intramuscular dimethyl sulphoxide (DMSO) causes the release of LDH into skin lymph, subcutaneous DMSO does not.5 That proportion of muscle LDH released during injury might represent the unbound or ;active' portion since no matter how severe the injury only about 1% of the total muscle LDH was released into the lymph.