The suddenness with which this pain comes on may be illustrated briefly by the following case:--A primigravida, aged 30, two months pregnant, was seized with sudden pain during a railway journey. Her condition became so alarming that she left the train at an intermediate station and placed herself under the care of a doctor whom she knew. A large, tender, and increasing swelling was found in the abdomen. The doctor regarded the patient’s trouble as being due to rupture of a tubal pregnancy. He asked me to see the patient, and I found a large swelling on the right side of the abdomen reaching as high as the liver. I considered that some change had taken place in this tumour consequent on the pregnancy: it was also probable that it might be an ovarian cyst which had twisted its pedicle. The swelling was very tender. On opening the abdomen the tumour proved to be a large subserous fibroid undergoing red degeneration. The gravid uterus contained several fibroids of the interstitial variety: it was removed. These fibroids exhibited the red change in streaks. It is a curious and noteworthy fact that many of the operations tabulated on pp. 81 and 82 were undertaken on an erroneous diagnosis. In some the acute pain and tenderness of which the patients complained led the surgeons to believe that the troubles were due to an ovarian cyst which had twisted its pedicle, or to the bursting (or abortion) of a gravid Fallopian tube. Practitioners and obstetricians are now becoming familiar with the fact that when a pregnant woman, who has also fibroids in the uterus, complains of sudden acute pain, it may be due to one of the fibroids undergoing red degeneration. [Illustration: FIG. 23. A GRAVID UTERUS IN SAGITTAL SECTION. The woman miscarried at the seventh month: delivery was obstructed by a cervical fibroid. The parts were removed by total hysterectomy. The small fibroid is in the condition of red degeneration (_Museum, R. College of Surgeons_). Half size. ] The cause of this change is unknown. Lorrain Smith and Fletcher Shaw, after an examination of four specimens, three of which were associated with pregnancy, believe that the change is due to thrombosis of the vessels of the fibroid. In two tumours they isolated micro-organisms, _e.g._ _staphylococci_ in one and _diplococci_ in another: the patients with these tumours exhibited toxic symptoms. In my early investigations of this disease I often took the tumours to the bacteriological laboratory with the hope of finding some micro-organism which would account for the degeneration. The results were so persistently negative that the search was abandoned. Since learning that Smith and Shaw had found micro-organisms in two cases I had the next specimen which came to hand examined, and it happened to be the fibroid obtained from the acute case described on p. 79. From the softened parts Mr. Somerville Hastings succeeded in obtaining _staphylococcus pyogenes aureus_ in pure culture.