My first object in this paper is to describe a particular variety-of delirium, one which differs from other varieties in the extent of the patient's disorientation: Whereas in other varieties the patient is disoriented in the three spheres of time, place and person, disorientation in the variety to be described is restricted to, or is most pronounced in, the sphere of time. Reasons will be given for regarding this variety as a rudimentary form of delirium, a "partial" or incomplete delirium, while that with disorientation in all three spheres is a severe or complete delirium. My second object is to show that in partial delirium the restriction of disorientation to the sphere of time is not a capricious and incomprehensible phenomenon but is understandable in the light of Hughlings Jackson's theories of nervous function and is indeed an especially clear illustration of the merit of those theories. Three cases