In the interval between the two plugs the sinus is freely laid open, all clot and granulations being gently curetted and washed away. Some bleeding may take place during these procedures, from the mouths of certain vessels entering the sinus between the two compressed regions. This is in itself a favourable symptom, insomuch as it proves that the thrombotic process has not extended in those directions. This hæmorrhage may be controlled with gauze plugs. The parietal sinus wall in direct relation to the thrombus is freely cut away, after which the whole field is lightly packed with gauze and the ear sewn back into position. The main portion of the wound is left open, the sinus plugs being brought to the surface whilst those inserted into the combined middle ear and antrum emerge from the external auditory meatus. All gauze-plugs may be withdrawn after twenty-four to thirty-six hours, the wound cleansed and lightly repacked. This process is continued daily till all is healed. _When the clot extends into the jugular bulb, and when the jugular vein appears to be involved_, it is necessary to expose and ligature the vein in the neck, thus preventing further extension of coagulation and diminishing the risk of general infection. This measure should be carried out before the lateral sinus is laid open. With fresh gloves and another set of instruments, the vein is exposed so as to allow the application of two ligatures, and the division of the vessel between those two ligatures. If possible, the ligatures should be applied above the level of the entrance of the common facial vein. In all cases, however, the application must be carried out, if possible, below the lower limit of the thrombus. After the vein has been divided, the upper end may be dissected in such a manner as to allow of its being brought to the surface of the wound and there anchored. Elsewhere the neck-incision is sewn up and protected with collodion gauze. The surgeon then returns to the mastoid and sinus regions, completing the exposure of the sinus and laying it open freely to the surface. At the termination of these procedures, an attempt may be made, by irrigation between the open sinus above and jugular vein below, to wash away all thrombus contained in the intervening portion of the vessel. Finally, both sinus and aural regions are packed with gauze, in a manner similar to that described above. Dressings are reapplied as circumstances demand, and the wounds allowed to heal by granulation. The great frequency of a streptococcus pyogenes infection justifies one in the early administration of anti-streptococcic serum (20 to 40 c.c. of Burroughs Wellcome’s ‘Pyogenes’) followed by an autogenous vaccine as soon as that can be prepared. MAIN POINTS IN THE DIFFERENTIAL DIAGNOSIS BETWEEN