One of the most singular features in the history of the filaria is its nocturnal habit. It is found in the blood only at night, unless, as Mackenzie has shown, night be converted into day--that is, if the hours of sleeping and waking be reversed. In Mackenzie's case the worms appeared about seven o'clock in the evening, increased up to midnight, and disappeared by eight or nine o'clock in the morning. What becomes of them at the time when they are undiscoverable in the blood is as yet unknown. Acknowledging filariæ to be the essential cause of chyluria, the precise method in which they operate to cause the obstruction, dilatation, and rupture of the lymphatics is a matter of speculation. The embryo filariæ are so lithe and small that they move among the corpuscles {119} apparently without harming them, but the ova in which the embryos lie coiled up, and which are often discharged unhatched, are large enough to cause obstruction in the smaller lymphatics and lymph-passages of the lymphatic glands, and thus cause the phenomena of chyluria, as well as of the other diseases of the lymphatic system with which it is often associated, or which may occur independently of it, such as elephantiasis, cutaneous lymph-vesicles with their chylous and lymphous discharges, lymph scrotum, chylous hydrocele, and other diseases of the lymphatics. Indeed, the total number of affections other than chyluria which are found associated with filariæ exceed those of chyluria. Among the diseases with which it is said to be associated is erysipelas. It is evident, therefore, that notwithstanding the fact that the discovery of the Filaria sanguinis hominis has shed a flood of light upon the subject of chyluria, the fact must not be overlooked that not a few cases of the disease have occurred in which the most careful search has failed to find this parasite in the blood. Careful examinations, during waking and sleeping hours, have been made without result, so that we cannot deny altogether the possibility of the disease occurring independent of filariæ as the cause. It is common, therefore, to speak of parasitic and non-parasitic chyluria. On the other hand, the filaria embryo is often found in the blood of persons apparently in perfect health. Manson tells us that out of every ten Chinamen taken at random, at Amoy, the blood of one will contain filariæ. MORBID ANATOMY.--There can hardly be said to be any morbid anatomy of chyluria, unless we regard the lymphatic lesions which sometimes accompany it as a part of the disease. Again and again do we read the reports of autopsies at which the kidneys were found normal, and where lesions have been noted they were such as are found due to other causes, and the coincidence was accidental.