One of the most striking features of the disorder is the difficulty of backing. In some cases he will back a few steps and then prove unable to back farther; in others he will show it best when heated with a journey; in other cases still he will back well enough under his own weight, but prove utterly unequal to the act if a heavy man is placed on his back, or if hitched to a loaded wagon. In backing with or without a rider the horse, pulled back by the reins, inclines backward with his hind limbs extended forward beneath the abdomen, his forefeet extended in front, and his back arched; he extends his head or turns it to one side, and when the change in the centre of gravity endangers his equilibrium, he draws back his forefeet without lifting them, each making a groove in the ground, and at the same time he makes a disorderly motion of the hind limbs to one side to restore the balance. In default of this he may drop his quarter on the ground and perform a back somersault on his rider. Even when he succeeds in balancing himself after dragging the forefeet back, the difficulty of further backing is rather increased, as the nervous irritability is enhanced by a continuance of the excitement. When hitched in a carriage the phenomena are virtually the same; when backed he extends or flexes the head, inclines the body backward, and after a time loses his equilibrium, sometimes executes a few disorderly steps backward, or throws himself violently to one side, or turns over backward in the shafts. The symptoms are always worse during hot, damp weather, and when the animals are exposed to the full glare of the sun. The milder cases can be worked without great inconvenience in winter, while they become utterly useless in summer. Active exertion and increased rapidity of the circulation has a similarly injurious effect. After a period of rest nothing amiss may be noticed, while after a period of work in the sunshine the symptoms become well marked and the difficulty of backing pronounced. Plethora or full feeding aggravates, while spare, laxative diet, laxatives, rest or bleeding relieves. The affection may become complicated by more active inflammatory action leading to paroxysms resembling those of meningo-encephalitis;—pushing against the wall, rearing up with the fore feet in the manger, acting as if walking or trotting, etc. In other cases the paroxysms resemble those of vertigo; the animal plunging forward, starting to one side, or rearing up and falling back.