Abstract
The main object of this review is to review the work on the biochemistry and microbiology of the rumen that has appeared since the beginning of 1952 when Owen reviewed thi subject. The following areas are considered; ruminant saliva, rumen bacteria, rumen protozoa, cellulose digestion, other carbohydrates, the volatile fatty acids, lactic and succinic acids, the metabolism of non-protein nitrogen and vitamins.