ABOMASUS, ABOMASUM, or ABOMASIUS, names of the fourth stomach of ruminating animals. The first stomach is called venter, the second reticulum, the third omasus, and the fourth abomasus. The third stomach, omasus, is endued with the singular quality of curdling milk. But the truth is, the stomachs of almost all animals, whether they ruminate or not, will produce the same effect, though not perhaps in an equal degree, as the stomachs of calves or lambs. See MILK, RUNNET.