In this form of paralysis one lateral half, the right or the left side of the body, is involved. It is a rare affection in the horse, but in man it is one of the most common forms of the disease, and usually appears suddenly in what is commonly known as a " stroke". The parts affected in hemiplegia are the fore and hind extremity, the muscles of the face, especially those of mastication, and the tongue on one side.
The loss of power may either be complete or incomplete, according to the intensity and extent of the cause, which commonly arises out of rupture of the vessels of the brain, with more or less escape of blood into the tissues of the organ.
Hemiplegia is usually sudden in its onset. The affected animal falls to the ground in a more or less unconscious condition, and the limbs on the paralysed side are incapable of movement. In a case quoted from M. Gerard by Percival the sensibility of the left, the affected side, proved extremely acute. The lips and alee of the nose were drawn to the right side, the contrary to that to which the head and neck turned. A blowing noise was made by the air in its passage through the nostrils. The left ear was paralysed and the tongue distorted. When oats were laid before the horse it seized them with the right side of the mouth, the left remaining motionless. There was great difficulty in mastication, and some of the food was not swallowed, but became lodged between the cheek and the molar teeth. In feeding, the horse plunged its muzzle into the middle of its food and opened its mouth wide. In drinking, its mouth was thrust deeply into the water. It could walk, but could hardly sustain itself after but a short exercise. On the fourth day the animal was unable to stand, sank down, and after several ineffectual struggles to rise, rolled over and lay upon its right side. Its pulse and respiration remained undisturbed. It died on the seventh day.