We know from Statistics that these Deaths occur, but why they occur and why they vary are questions not yet to be fully answered in our present stage of knowledge (or of ignorance). At one time a sufficient cause seems to present itself; but the very next outbreak of Puerperal disease may occur under quite different conditions. For years an Institution may escape excessive Mortality; and then it may suffer severely under the same apparent circumstances. All that we can do at present is to see whether there are removable causes in cases where the Mortality is excessive, and to remove them. Fully recognising how much we have need of caution, this subject will be next considered generally and as far as possible in its practical bearings on the points at issue. There are some important remarks in Dr. Le Fort’s book, bearing on this subject, which may find a place here. _Puerperal Fever._—Dr. Le Fort states, as the result of his enquiry, that the frequency of obstetrical operations modifies the general mortality only in a slight degree; that the excessive mortality in lying-in hospitals is much greater than can be attributed to ordinary hospital influences; that it depends neither on the social condition of the women, nor on the moral conditions under which delivery may occur; that it may be more or less influenced by the insalubrity of particular hospitals, but that puerperal fever is the principal cause of death after delivery; that this disease shows itself in all hospitals, in all maternity institutions, in all climates, in the south of France as it does at St. Petersburg, in Dublin as in Vienna, in London as in Moscow. It exists in America as in Europe. It is less frequent and fatal during the summer months, attributable in part at least to greater facilities of ventilation following on higher temperature (in other words, to having your windows open instead of shut). This disease develops itself spontaneously under certain unknown circumstances. When it is about to become epidemic, it is sometimes preceded by the prevalence of erysipelas. Dr. Le Fort points out that what was considered a severe epidemic in the British Lying-in Hospital, in the year 1770, is ‘unfortunately less than the _mean_ mortality of the Maternité at Paris.’ While admitting that puerperal fever may originate _de novo_, Dr. Le Fort dwells strongly on the communicability of the disease as an efficient cause of its prevalence. He adduces opinions of the following physicians—Oppolzer, Rokitansky, and Skoda, of Vienna; Virchow, of Berlin; Lange, of Heidelberg; Schwarz, of Göttingen; Löschner, of Prague; and Hecker, of Munich—on the nature and origin of this fatal disease. Generally they testify to the propagation of puerperal fever by contagion, but they also state that it is a blood disease—a product of foul air, putrid miasms, and predisposition to malignant inflammatory action.