The contributions made by American physicians to the knowledge of typhoid fever have been both numerous and important. In 1824 it was described by Nathan Smith[14] under the name of typhus fever of New England, and in 1833, E. Hale, Jr.,[15] of Boston, published in the _Medical Magazine_ for December an account of three dissections of persons considered by him to have died of the disease. In reference to these cases, Bartlett[16] says that if the diagnosis could be looked upon as certain and positive they would constitute the first published examples of intestinal lesion in New England. In February, 1835, William S. Gerhard of Philadelphia, who was then under the impression that the two diseases were identical, reported two cases under the name of typhus fever, the symptoms and post-mortem appearances of which he showed differed in no respect from those he had been accustomed to see in the cases of typhoid fever he had observed with Louis during his studies in Paris. The year after Gerhard had, however, the opportunity of observing an epidemic of true typhus fever, and was at once struck with the difference between the symptoms of the cases which then fell under his care and of those he had seen in Paris. In an admirable paper which appeared in the numbers of the _American Journal of the Medical Sciences_ for February and August, 1837, he points out very clearly the differential diagnosis between the two diseases. He particularly insisted on the marked difference between the petechial eruption of typhus and the rose-colored eruption of typhoid fever. He showed that the latter disease was invariably associated with enlargement and ulceration of Peyer's patches and with enlargement of the mesenteric glands, and that these conditions were never presented in the former. He also fully recognized the fact that typhus fever was eminently contagious, while, on the other hand, he was fully aware that typhoid fever was not contagious under ordinary circumstances, "although in some epidemics," he says, "we have strong reason to believe it becomes so." The appearance of this paper marks an epoch in the history of typhoid fever. Murchison, when speaking of it, says that to Gerhard, and Pennock (who was associated with Gerhard in his observations) certainly {241} belongs the credit of first clearly establishing the most important points of distinction between this disease and typhus fever, and M. Valleix alludes to it in terms equally complimentary. It is undoubtedly owing to it, more than to any other cause, that the differential diagnosis of these two diseases was perfectly understood by the great body of the profession in this country long before the question of the relation which they bore to each other was definitely settled in Great Britain,[17] or even in France. [Footnote 14: _Medical and Surgical Memoirs_, Baltimore, 1831.] [Footnote 15: _Observations on the Typhoid Fever of New England_, Boston, 1839.]