cullen's understanding of the nervous system was also influenced by his contemporaries, one of whom was albrecht von haller (1708–1777). haller proposed that tissues, including muscles, were characterized by "irritability" (or contractility), while nerves were characterized by "sensibility" (or feeling). using haller's characterization, cullen defined disease "as an excess or deficiency of sensibility." however, cullen interpreted sensibility as "muscle mobility and vigour" and diseases were caused by the imbalance of irritability and sensibility. based on this definition of disease, his therapeutics "either stimulated or sedated the nervous system." he categorized diseases into four main classes: pyrexiae, neuroses, cachexiae, and locales. within the classes were nineteen orders and 132 genera. the four orders of neuroses were comata, adynamiae, spasmi and vesaniae. comata was defined as "a diminution of voluntary motion, with sleep, or a deprivation of the senses." adynamiae is defined as "a diminution of the involuntary motions, whether vital or natural." spasmi was defined as "irregular motions of the muscles or muscular fibers." vesaniae was defined as "disorders of the judgement without any pyrexia or coma."