Horner's syndrome in the dog and cat as an aid to diagnosis.

Four cases of Horner's syndrome, two in dogs and two in cats, are described. Miosis, ptosis, and enophthalmos were present in three of the cases and in addition, protrusion of the nictitating membrane was present in the fourth case. In the two cases described in cats, there was also evidence of peripheral vasodilation in the skin of the face on the same side as the Horner's syndrome.