The marked differences found in the process of digestion of other vertebrates are as follows:
1. Salivary digestion or buccal digestion, which is characteristic of mammals, is rarely found in other vertebrates but the saliva f frog, toad and of the fowl contains an enzyme called amylase
2. The pepsin of mammals differs in specificity from that of salmon.
3. In gold fish, lizard and some passerine birds there is found an enzyme called chitinase which is completely lacking in mammals. This enzyme helps in the digestion of chitinous materials contained in food.
4. The birds, such as honey guides (indicator), like mammals, do not produce esterase enzyme but are dependent on their microflora.
5. In mammals the medium of stomach is acidic, it is due to the secretion of hydrochloric acid but in some rays and bony fishes the medium of stomach is alkaline even though the pepsin is present.
Soifle sharks, by contrast, have been reported to have an acidity twice that of man.
6. There are several vertebrates such as holocephali, dipnoi, teleosts and protochordates which donot possess stomach and, thus, pepsin is not secreted.
7. In fowl preliminary digestion takes place in the crop by autolysis and bacteria.
8. In herbivorous animals special modifications are met in the alimentary canal that help in cellulose digestion.
In these animals cellulase is found which digests the cellulose. Cellulase is not secreted by the animals but is produced by the bacteria present in the alimentary canal.