The psychical symptoms are shown by errors of judgment. The animal becomes dull and spiritless and wanders about half dazed. The mental dullness passes into stupor. This dull, stupid condition has been compared to intoxication with opium. If the locoed horse is led across a stick lying on the ground he often jumps high as if it were a great obstacle. The animal may now have maniacal attacks, during which he rears and may fall backward,[42] and makes unreasonable jumps and other unexpected movements, thus rendering himself dangerous to man.[43] Other symptoms due to disturbances of the central nervous system are hallucinations of various sorts. Though the optic nerve itself is apparently not affected, the animal will stare at an object for a long time without any apparent comprehension of its nature. This disturbance in the visual function McCullaugh claims to be one of the first symptoms of this disease. The animal seems to lose all idea of distance, as he will butt against an obstruction as if oblivious of its presence. Any sudden or violent motion made before him may cause him to fall. According to some, the animal loses the sense which guides him in finding water. A cow may fail to recognize her calf.[44] There is more or less loss of control of the limbs[45] and tremors;[46] the feet are lifted abnormally high when trotting, and, if crowded, the animal falls headlong and will jump over little hollows as if they were wide ditches.[47] The horse may shy without apparent cause and kick at imaginary objects,[48] and, in fact, the reasoning powers seem to be lost. These attacks are brought on by sudden excitement or when crossing water.[49] There may be cutaneous hyperæsthesia. The animals may remain with the herd, but they often wander away. Stalker records the following observations: I have seen a single animal miles away from any other individual of the herd, carefully searching as if for some lost object, and when a loco plant is found he would devour every morsel of it with the greatest relish. As soon as one plant was eaten he would immediately go in search of more, apparently oblivious to everything but the intoxication afforded by his one favorite article of food.[50] All of Nockolds's animals which were locoed were mares more than 6 years of age.[51] According to Stalker there is a passive type in which the animal shows symptoms only on being disturbed; the animal then becomes unmanageable. This happens even with old, well-broken saddle horses.[52]