A most interesting group of cases has been recorded by Weil,[10] where out of a family of 91, 28 were polyuric. The head of the family, a polyuric, lived to the age of eighty-three, while his descendants were robust, many of them attaining a good old age. There were no anomalies of the circulation, and the persons affected were not alcoholics. Their only complaint was of a troublesome thirst, and they declined treatment. [Footnote 10: _Cbl. für die Med. Wiss._, 1884, p. 263, from _Virch. Arch._, xcv.] The PATHOLOGY of diabetes insipidus, so far as is positively known, may be gathered from the previous account of its etiology and symptoms. It is evidently of nervous origin in the great majority if not all cases. It is often connected with distinct lesions of the nervous system, and attended with other nervous symptoms. In some cases it occurs in connection with a well-marked hysterical diathesis. The copious flow of pale urine as a sequel to the hysterical paroxysm is well known, and the same thing often attends a severe nervous headache in either sex. It is probable that the polyuria attending lesions of the urinary passages is a reflex nervous phenomenon, since it may be present when there is no suspicion of organic renal disease. Guyon[11] states that surgical polyuria occurs under three {32} conditions--painful excitation of the sensibility of the deeper portion of the urethra or the vesical mucous membrane; repeated attempts to urinate during the night; retention of urine more or less complete, but especially when there is distension of the bladder. Of the first cause he gives an instance in the case of a young man who had a polyuria whenever a bougie was passed beyond a urethral stricture. [Footnote 11: _Leçons cliniques sur les Maladies des Voies urinaires_, Paris, 1881.] Where, however, polyuria, especially chronic, is due to habitual over-distension, it is in the highest degree probable that it is at least partly due to structural alteration of the kidney. The well-known experiment of Bernard, by which an increased flow of urine was induced by a puncture of the floor of the fourth ventricle, and those of Eckhard on section of the splanchnic nerves, show how it is possible for nervous affections to influence the secretion of urine, though the path or paths of the influence are by no means completely made out.