Ultrasonogram of the rumen. Ultrasonogram of the rumen showing the transition between the dorsal gas cap and ingesta layer viewed from the 12th intercostal space on the left side of a nine-year-old Swiss Braunvieh cow. The rumen wall appears as a hyperechoic line. Reverberation artifacts, which run parallel to the ruminal wall, reflect the gas cap and end abruptly at the transition to the fibre mat. 1 Abdominal wall, 2 Rumen wall at the level of the dorsal gas cap, 3 Rumen wall at the level of the fibre mat, 4 Transition between 2 and 3, Ds Dorsal, Vt Ventral.