=Individual and racial mental dullness and torpor= must also be recognized. Some are stupid and slow, others alert and quickly responsive. Some horses are not _level-headed_ and become uncontrollable in difficult situations. Some dogs are so emotional as to endanger their lives from sudden heart trouble. Some horses, dogs and cats will pine and die when separated from their fellows or human friends. Extreme timidity, or sudden rage may be so marked as to constitute a virtual morbid phenomenon. Sluggish cerebral and mental action may result from _exhaustion_, _prostration_, or _dementia_; also from _cerebral congestion_, _pressure_ and _degeneration_; or from _poisoning by narcotics_, _ptomaines_ or _toxins_ (opium, hyoscyamus, Indian hemp, dourine, milk sickness, etc.). It may come from profound absorption in another object, as when the rabid dog bears whipping without a howl. =Delusions= or =hallucinations= are shown in the rabid dog snapping at flies, or attacking his friend or master as an enemy, as well as in other forms of delirium. Narcotics, such as opium, Indian hemp, etc., ptomaines, toxins, and (in dogs) essential oils cause delirium by acting on the nerve centres. =Vice= in its various forms may become a genuine neurosis, the animal losing control of its actions. =Violence= in the form of self-defence or aggression is seen in mares in _heat_, in bulls or stallions under sexual excitement, in animals roused by inconsiderate whipping, or in bulls looking on scarlet clothing. Some high-spirited animals, under extreme fatigue from overwork, sometimes become violent but resume their docility under rest and food. In all cases we must know the normal of an individual animal to enable us to properly appreciate any apparent deviation from the psychic norm. No less essential is it to take into account the environment and treatment of the patient. With regard to localization of cerebral lesions, Sequin thinks emotions are probably generated in the basal ganglia such as those of the pons and thalami, while inhibition depends on the anterior cerebral cortical convolutions. DIAGNOSIS, SYMPTOMS AND THEIR IMMEDIATE CAUSES. LOCALIZATION OF LESION IN SPECIAL SYMPTOMS.