Free fructose in normal mammalian tissue has been shown to occur only in certain accessory sexual tissues of rodents,1 in sheep seminal vesicles,2 and placenta of ungulates.3 As a result of secretion by the seminal vesicle fructose is a normal constituent of semen in many animals.4,5 Fructose also occurs in the fetal blood of ungulates,6 arising by a process involving sorbitol as an intermediate.7 Its occurrence in lenses of rats8 and rabbits8,9 appears to be an exception to the generalization that free fructose is normally found only in tissues associated