The progress in pathology which observers were making was temporarily impeded about this time by the fact that while typhoid fever was of frequent occurrence in Paris, typhus fever was comparatively rarely met with and had not been epidemic there for several years. Bretonneau, Louis,[12] Chomel, and indeed the greater number of contemporary French physicians, therefore fell into the error of supposing that the fever which was then common in England was identical with that which they were describing, while the English physicians of the period, with but few {240} exceptions, contended with equal strenuousness that there was but one form of continued fever, and that this was very seldom associated with disease of the intestines. In the second edition of his work Louis abandoned his former opinion, and admitted that the typhus fever of the English was a very different disease from that which formed the subject of his treatise; but the confusion which existed in England in regard to this disease was not completely dispelled until the appearance in 1849 and the following two years of several papers on this subject by Sir William Jenner,[13] in which it was conclusively demonstrated that typhoid and typhus fevers were separate and distinct diseases. In Germany, however, the non-identity of these diseases was recognized as early as 1810. Murchison says that the names by which they are still generally known in that country, typhus exanthematicus and typhus abdominalis, were given to them not long after. [Footnote 12: _Researches Anatomiques, Pathologiques et Therapeutiques sur la Maladie connue sur les Noms de gastro-entente, etc._, par P. C. A. Louis, Paris, 1829.] [Footnote 13: _Med. Chir. Trans._, vol. xxxiii.; _Edinburgh Monthly Jour. of Med. Sci._, vols. ix. and x., 1849-50; and _Med. Times_, vols. xx., xxi., xxii., xxxiii., 1849-51.]