The biological concept of mental disease propounded by Hughlings Jackson in his Theory of Evolutional Levels will help in the understanding of the causes and symptoms of insanity—dissolution of the highest level bring ing into relief lower levels. Thus a negative condition of the highest evolutional level of control permits of over-action of the lower level of ideation, e.g., the delirium of fever. In mental disorders there may be a negative condition of the highest level of control with disordered ideation manifested by hallucinations and delusions, owing to partial disintegration of the psychic unity. Such hallucinations and delusions may determine various active uncontrolled and irresistible impulses—disorders of con duct. When the disease has sunk to a lower depth of dissolution of evolutional levels there may result emotional indifference and apathy reflected in a mask-like expression, and motor inertia or katatonic stupor with flexibilitas cerea. Stuporose states with mental confusion indicate a more diffuse toxic influence on evolu tional levels and are more hopeful of recovery than the persistence of hallucinations and delusions, the mind remaining clear.
These do not play an impor tant part per se in the production of the true insanities. They may, however, act as exciting or contributory causes in individuals with an hereditary latent tendency. Stress per se from disease and disasters of every kind cannot be the important factor believed to be in the production of the true insanities as distinct from organic brain disease, e.g., general paralysis and lethargic en cephalitis. This was clearly shown during the World War by the fact that Bonhoffer, an eminent Austrian psychiatrist, only found five insane among I0,000 Serbian prisoners.
Organic brain disease may cause various symptoms of irrita tions such as fits, headaches, pains, stiffness of muscles, and delirium or drowsy stupor, loss of memory, paralysis and demen tia, according to the pathological process and the structures affected.