“…More recent evidence from Herpol (1964Herpol ( ,1967 indicates that pepsin is present in the proventriculus of all grain-eating species investigated and even in the gizzard of certain carnivorous species such as Falco tinnunculus (falcon) and Buteo buteo (buzzard) (Herpol, 1964). Before birds are fed, the pepsinogen granules are abundant in the gastric mucosa; shortly after feeding they virtually disappear, however, indicating that they are concerned in digestion.…”