The early opinion that the internal coat of the larger blood vessels of man is immune against tuberculous disease has been abandoned since the well known researches of Weigert1 concerning the origin of general miliary tuberculosis from tuberculous foci in the walls of pulmonary and other veins. It is now generally known that in tuberculous leptomeningitis, for instance, there occurs a marked tuberculous disease of the small arteries.
When the walls of the blood vessels, particularly the larger branches, become tuberculous, then it is due, in the majority of cases, to direct extension of the process from a tuberculous focus in the vicinity of the wall. Independent tuberculous disease of the vessel wall is much rarer; in the majority of the cases it must then be regarded as of hematogenous origin. In the later stages, however, of such foci it is usually impossible to say whether the disease began