1. The main function of the omasum is to represent an arrangement for continuance of the fermentation in all species.
2. The pH of omasal contents of sheep and cattle is near neutral and the rate of fermentation equals the rate in the rumen.
3. Omasal contents of deer have a lower pH and show a lower fementation rate when compared with the rumen and small amounts of soluble carbohydrate accumulate, contributing not more than 0·3 g of glucose to the animal per day