I have thought that its origin might be accounted for on the principle of metastasis of morbid material. The patient had pneumonia which passed through its several stages somewhat rapidly, resolution taking place about the end of the second week. The symptoms of this were well marked, viz: a chill followed by fever, cough, brick-dust sputa, delirium, pain over lower half of right lung, which was solidified, and afterward gave the crepitant and sub-crepitant roles. Could not the morbid material, which entered the circulation from the re-absorption of the deposit in the solidified lung, have been carried to the synovial membrane of the knee, and there found a lodgment, and set up the inflammation which resulted in the formation of so much pus? If not, Why not? Notwithstanding a tedious illness, and an anchilosed knee, was not this result better than to have had suppuration of the lung tissue and destruction of the whole of the right lung, and perhaps eventually the left also? However, we are not certain that such a result would have followed, although the patient's general appearance at the time of the attack, and the typhoid condition which followed, as also the low grade of inflammation bordering on the scrofulous, made such a thing probable. CASE FOURTH.--On Jan. 31st, 1879, Mr. R----, Italian, aged 35 yrs., while chopping wood near Almaden mines, was injured by a falling tree. The lower part of the body was very much bruised, both posteriorly and anteriorly. The only place where the skin was broken was a smooth cut about four inches long and nearly half an inch deep, following the fold or crease between the right testicle and thigh, and extending from the anterior part of the testicle to the perineum in a straight line just where the scrotal integument joins that of the thigh. The main injury was in the lumbar region over the upper lumbar vertebrae. The spinous process of the lower dorsal vertebra seemed to be unusually prominent, leading to the supposition that the spinous process of the upper lumbar vertebra might be fractured and depressed. However, I was unable to detect mobility or crepitus in any of the processes, spinous or transverse, either of the dorsal or lumbar vertebrae. There was considerable tenderness over the lumbar region. I would here state that the examination was made about twenty hours after the receipt of the injury. There was but little discoloration of the skin, not very much pain, no paralysis of any part, the bladder evacuating itself naturally, and a cathartic producing its ordinary effect in the usual time. The patient did well; complained of but little pain; did not use opiates. On Wednesday and Thursday following, the patient felt well enough to walk about the wards, eating well and having no constitutional disturbance, pulse never higher than eighty per minute, and the temperature not above 99 degrees F.