_Frequency in different animals._ The affection is far less frequent in the domestic animals than in man, doubtless because of the absence of the special susceptibility which attends on the more highly specialized brain, the disturbing conditions of civilization, and the attendant vices. Among domestic animals, dogs are the most frequent victims in keeping with their relatively large cerebral development, their emotional and impressionable nature and the unnatural and artificial conditions in which as house pets they are often kept. Their animal food and the consequent uric acid diathesis is a probable cause, as it is in man. In ten years of the dog clinic at Alfort they made an average of 3 per cent. of all cases. Next to the dog the pig kept in confinement is the most frequent victim, while cattle and horses come last. At the Alfort clinic epileptic horses were not more than 1 per 1000 patients. It is not at all infrequent in birds, especially canaries and parrots. Reynal has seen it in sparrows. _Divisions._ The disease has long been divided into _petit mal_ and _grand mal_ (_haut mal_). The =petit mal= (slight attack) is usually a transient seizure affecting a group of muscles only and associated with only a momentary or very transient loss of consciousness. The loss of consciousness is uncertain as to many cases. Under partial epilepsies must be included the hemi-epilepsy, or Jacksonian epilepsy, which is confined to one side of the body. The =grand mal= (severe attack) is one in which the loss of consciousness is complete, and the convulsions are general in the muscles of animal life. Another division is into =symptomatic= and =idiopathic= cases, and if this distinction could always be made it would be of immense value in the matters of prognosis and treatment as the removal of the morbid state of which epilepsy is the symptom will usually restore the patient to health. Thus the removal of worms from the alimentary canal, of indigestible matters from the stomach, of a depressed bone or tumor from the surface of the brain may in different cases be the essential condition of a successful treatment. _Morbid Anatomy and Pathology._ The literature of epilepsy is very rich and extensive and yet no constant lesions of the nervous system can be fixed on as the local cause of the disease. A review of the whole literature leads rather to the conclusion that irritations coming from lesions of the most varied kind, acting on a specially susceptible brain will rouse the cerebral centres to an epileptic explosion. Thus epilepsy has been found to be associated with lesions of the following kinds: 1st. Brain lesions of almost every kind, including malformations. 2nd. Lesions of the walls of the cranium. 3d. Disorders of the cerebral circulation. 4th. Lesions of the spinal cord. 5th. Morbid states of the circulating blood (excess of urea, uric acid, creatinin, lead poisoning).