ocular paralysis, or an Argyll-Robertson pupil may exist as an isolated symptom for a considerable time, presumably for years; (2) that any two of these may be associated together, with a correspondingly increased presumption that the diseased process causing them is of the locomotor ataxia order; (3) that any one of the three, or a combination of two or all of them, may exist in conjunction with a greater or less degree of evidence of spinal disease; and (4) that occasionally a case which commences with purely ocular symptoms may be seen to develop with comparative rapidity characteristic symptoms of the spinal lesion of locomotor ataxia. The cases therefore may be held to justify the view that an optic-nerve atrophy, an ocular paralysis, or the Argyll-Robertson pupil (not capable of other explanation) must be regarded as affording a definite basis for suspicion in reference to a possible development of spinal disease. On the other hand, it must be admitted that the prognostic indication, so far as spinal disease is concerned, is not an absolute one, for the ocular defect may exist certainly for many years without any evidence whatever of the involvement of the spinal cord. The cases here recorded have all been the subject of detailed and in most cases repeated examination, and unless the contrary is stated, it may be taken for granted that the thoracic and abdominal viscera are normal, to physical and other methods of examination. In all cases, too, in which no specific statement is made, it is to be understood that the visual acuity, the visual fields (both for white and colors), and the fundus oculi have been proved to be normal. This last statement of course does not apply to cases in which optic atrophy exists. Particular care has been taken to be accurate in regard to the condition of the pupils and the knee-jerks. In nearly, if not absolutely in every instance where a departure from the normal is chronicled, the record has been confirmed by more than one observer, and in the case of a deficient knee-jerk the conclusion stated has never been formulated until the conditions insisted on by Gowers, Buzzard, and Jendrassik have been fulfilled. With a few exceptions in which only a single observation was possible, the patients have been watched for months, and in some instances for several years. The cases are arranged in series, with a view to show how, from a purely ocular condition, one may pass through gradually accumulating evidence to the same ocular condition in association with the characteristic signs of the spinal lesion of locomotor ataxia. I.—CASES IN WHICH OPTIC-NERVE ATROPHY IS THE PRIMARY OR DOMINATING CONDITION. (_a_) _Optic Atrophy, without Other Evidence of Disease._