The history of previous investigations and the fluctuations of opinion are excellently given by Dr. Murchison in his great work on the “Continued Fevers of Great Britain,” 1862, 2d ed. 1873. Dr. H. C. Lombard of Geneva appears to have been the first to state positively (in 1836) that “there were two distinct and separate fevers in Great Britain; one of them identical with the contagious typhus, the other a sporadic disease, identical with the typhoid fever of the French.” He failed, however, to point out the distinctive eruptions and other characteristics of the two fevers. At the same period Drs. Gerhard and Pennock in Philadelphia arrived at more definite conclusions, and distinguished the typhus of Philadelphia as being the same as British typhus, the old gaol, camp, and ship fever, so direfully contagious and fatal; while certain intestinal phenomena were invariably found in the other or typhoid fever, which was rarely contagious. The characteristic eruptions and many of the symptoms were also accurately discriminated. These observers were followed by others who with more or less success and emphasis insisted on the same views. Among these were Drs. H. C. Barlow and A. P. Stewart, both of whom read important papers on the subject before the Parisian Medical Society in 1840. In 1841 the celebrated Louis in the second edition of his great work on typhoid fever accepted the view that the English typhus was very distinct from the fever which he had so largely elucidated. Nevertheless many physicians of authority strongly maintained their identity, and the majority of the medical schools taught this doctrine, which could not fail to retard progress. It is obvious how much uncertain and injurious treatment must have existed for a long period owing to the confusion of these two diseases. In his series of papers published in 1849 and 1850 Dr. Jenner confirmed and extended the distinctions between the symptoms of the two fevers, comparing the selected cases most minutely as regarded previous health, complexion, sex, age, mode of attack, duration, eruption, expression during disease, manner, hue of face, presence of headache, delirium, loss of muscular power, sensation, appearance of the tongue, suffering of pain, appetite, thirst, pulse, cough, and lung symptoms, and many other particulars, and detailed most carefully the _post mortem_ appearances of the diseased action in every organ.