On November 5, 1799, having definitely decided to give himself wholly to the new calling, Nachtegall opened a private outdoor gymnasium in the yard of number 45 Østergade, the first institution in modern times devoted exclusively to physical training. The 5 pupils with whom he began had increased to 25 by the end of the year, and in the winter of 1803-04 the number reached 150, both children and adults, under six teachers whom he had himself trained. When in 1804 the King appointed him professor of gymnastics in the university he had already given, for two years, lectures on the history and method of physical training, with the help of a former pupil, to an audience made up of students there and in a college for teachers, with an admixture of military men. Meanwhile the training of military and naval cadets and the instruction in gymnastics given in schools for non-commissioned officers had also been entrusted to him, and when the King established a Training School for Teachers of Gymnastics in the Army (_det militære gymnastiske Institut_), by decree of August 25, 1804, Nachtegall became its first director. From this as a center the new teaching was to be spread throughout the entire army and navy, including the Norwegian regiments. Four years later civilians were also admitted to the courses, the institution now attempting to do for the schools and the people at large what it had already accomplished for the army, and to prepare instructors for teachers’ colleges and the elementary schools especially. The usual length of the course was fifteen to eighteen months, though the first pupil was graduated in August of 1809. By 1814 the civilian training school, caught in the stress of hard times, had ceased to exist. Meanwhile a total of only 31 students had completed its course, but 10 of these went out to occupy positions at _Seminarier_ (teachers’ colleges), and so became in turn the instructors of other teachers-to-be.