THiV following case is recorded partly because of its rarity, and partly to indicate its origin from the meningeal fibroblasts. In so doing some semblance of order has been given to what might otherwise appear to be an encapsulated tumor wholly unrelated to the other encapsulated tumors of the cerebrum. At the same time it has been rescued from the large group of tumors of unexplained origin.Case Report.-Motor and sensory jacksonian convulsions involving the right leg and trunk for three years in a man of forty-nine. Increasing frequency of attacks with eventual involvement of right arm. Examination revealed marked weakness of right leg and slight weakness of right arm with increased leg reflexes, ankle clonus and Babinski. Position sense was disturbed in the right hand and toes. Fundi showed no papillcedema; spinal-fluid pressure was seven millimetres mercury. A calcified tumor of the left parietal area was seen by X-ray. At operation a large calcified tumor attached to the falx along the longitudinal sinus was removed. It lay behind the central fissure. It was an osteochondroma. Improvement after operation. Recurrence four years later with a second removal of a similar tumor which was this time diagnosed chondrosarcoma. Improvement followed. Three further admissions for irradiation. Final admission six years after first operation, nine years after onset of symptoms, with recurrence of tumor seen in X-ray and with right hemiparesis. Removal of tumor. Death.History.-The patient, a man of forty-nine, was admitted to the service of Dr. W. G. Spiller in the University Hospital in May, 1921, complaining of jerking and lameness of the right leg. He had been well until September, I9I8, when he awoke one morning with a numb feeling in his right leg. Almost immediately after this his right leg began to jerk, followed by a sensation of jerking of the entire right side of his body. He thinks his right arm jerked, but is sure the face did not. The jerking continued violently for ten minutes, then ceased, only to begin again. After it ceased he felt numb over the entire right side of his body, a sensation which soon passed away. The next day the only residual was a feeling of heaviness in his right calf.One month later he experienced another attack involving the right leg. This began first with a throbbing sensation in the entire right leg, followed by a jerking which lasted four to five minutes, starting first in the foot and extending up the leg. This was followed by a few twitches in the right shoulder and chest. Attacks of this sort came on every month following this, preceded in each instance by a feeling of numbness over the entire right side, a few hours before the attack.In January, I921, the attacks occurred every week, milder in degree, but similar in nature to the more severe convulsions. In February, 192I, a particularly severe convulsion was followed by a temporary inability to use his right leg. After this the right leg became stiff so that he was unable to lift his heel off the floor. In April, I92I, after a ...