With =optic vertigo=, the attendant conditions will help to a diagnosis. The animal has come from darkness to full sunshine; there is the white, icy or snowy reflection everywhere which the animal was facing when attacked, or the glistening lake or river, the overdraw check rein, or the blind with perhaps a shining inner surface. The pupil is closed, and the eye is rolled back or oscillates in one direction or another. The symptoms are checked by covering the eyes or removing the subject into a dark building or even into the shade of a tree or shed. With =aural vertigo= there may be similar rolling of the eyes, without the pupillary closure, the ear may be drawn down or back, and the shaking or jerking of the head is likely to be a marked feature. If there is more motion of one ear than the other, if the head is jerked to the one side, if there is a measure of deafness in the one ear (to be ascertained rather in the intervals between attacks), if there is disease of the pharynx, the Eustachian tube or pouch, or swelling about the root of the ear, if there is wax, scurf, or acarus in the ear, if the animal rubs it frequently, aural vertigo may be suspected. =Nasal vertigo.= Those forms in which the head is jerked horizontally, vertically, or diagonally, the animal pressing against its mate or the pole, or outward in the harness, and getting out of its track, even if it should stop short of falling, and which appear only during work, or are aggravated by exertion, have been attributed to lesions of the ear (Fleming), but in some cases they can be warded off by wearing a net over the nostril, and can be entirely stopped by complete transverse section of the pes anserina, so that in a certain number at least they must be accounted nasal. These are not usually attended by sneezing. The simple expedient of driving with a rather close net over the nostril may enable one to diagnose many of the purely nasal forms. =Plethoric vertigo= may be suspected when the attack comes on in spring, in a fleshy or fat horse, overfed and little exercised, when there is dark red congestion of the nasal mucosa and conjunctiva, and a subsidence with rest. In the _vertigo_ of brain lesions, the acute forms are attended by fever and marked signs of delirium or disordered nervous functions, while in the chronic forms there may be permanent hyperæsthesia or anæsthesia, general or with rather diffuse limits, and the vertiginous attacks repeat themselves frequently irrespective of weather, though they may be precipitated by faults of feeding, indigestion, severe exertion, or some of the other exciting causes above mentioned.