"The male line, if clean, and the male calves, are used for sacrifice by the Egyptians universally; but the females they are not allowed to sacrifice, since they are sacred to Isis" (Herodotus, ii, 41). Rawlinson says, "in order to prevent the breed of cattle being diminished: but some mysterious reason being assigned for it, the people were led to respect an ordinance which might not otherwise have been attended to." He quotes Porphyry, De abstin. ii, 11, who doubtless was St Thomas's authority. The sacrifice and eating of bull beef in Egypt is described by Herodotus, ii, 40.

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