In study of Puerperal Sepsis has already been made by various observers and from different standpoints. There is however as much information yet to be obtained or confirmed on account of the available statistics being comparatively small. Thus having the control of a large number of patients, I have felt it a duty to endeavour to increase the list of cases of this most important subject. In private practice the opportunity for a systematic research is not great, and the total number of cases seen is relatively small in comparison with those of a large Maternity Hospital with, in addition, an External Department, in which nearly 2500 patients are treated in their own homes annually. Here numbers are obtained and it is possible to collect the cases throughout every month of the year, so that a consecutive list results. In addition to this, I have been unable to find any records of the Bacteriology of fevers of the Puerperium from the Maternity Hospitals of the Three Kingdoms. In reports obtained elsewhere, the investigation has been either a purely Bacteriological one or a Clinical, in which while following the course of each case in reference to treatment, no attempt has been made to ascertain the specific cause. In this study an endeavour has been made to combine these two aspects, the germ being demonstrated at the commencement of the pyrexia, and the case being followed to its termination with a record of the events as they occurred. Although in 1850 Sir J.Y.Simpson published a paper on the "Analogy, between Puerperal and Surgical Fever" and investigations have since proved the analogy, there are still many practitioners who fail to appreciate and even deny their identity, and who will attend a woman in her confinement without any, or but scanty attempts at aseptic precaution, while they will take considerable care before performing any surgical operation. Thus any additional information on the subject seems of some value. A number of inquiries have been made into the Bacteriology of the Vagina, both of non-pregnant and pregnant women, and various results obtained, but a fairly definite conclusion has resulted. Therefore I have not attempted to carry any investigations into this region, but have waited until~the condition of pyrexia manifested itself, and have then endeavoured to ascertain its cause in the simplest manner possible and directly from the uterus.