Surface rippling of the lower left flank of the cow: mirror of ruminal motility.

A detailed description is given of 5 types of surface ripples occurring on the ventral part of the lateral abdominal region of the healthy dairy cow. Results of endoruminal palpation and concurrent visual observation of healthy cows which have permanent ruminal fistulae indicate that the more apparent ripples are due to the movements and changes in tension of the underlying cranial and caudal parts of the left longitudinal pillar and the left accessory pillar of the rumen. The ripples occur during both the primary (or mixing) cycle and the secondary (or eructation) cycle of ruminal motility. The cause of the rising and sinking of the left paralumbar fossa is discussed, and a correlation is made between their occurrence and that of the surface rippling. The possible clinical significance of the rippling is considered.