Wagner's activity as a writer and worker was enormous, and his range extensive, most of his hard work having been done at Erlangen while his health was good. His graduation thesis was on the progress of the working classes. The ambitious title of
The historical development of epidemic and contagious diseases all over the world, with the laws of their diffusion showed the influence of Schönlein. His first treatise was
Die Naturgeschichte des Menschen (in 2 vols, Kempten, 1831). Frequent journeys to the Mediterranean, the Adriatic, and the North Sea gave him abundant materials for research on invertebrate anatomy and physiology, which he communicated first to the Munich academy of sciences, and republished in his
Beiträge zur vergleichenden Physiologie des Blutes (Leipzig, 1832–33, with additions in 1838). In 1834–35, he brought out a textbook on the subject he chaired (
Lehrbuch der vergleichenden Anatomie, Leipzig), which recommended itself to students by its clear and concise style. A new edition of it appeared in 1843 under the title of
Lehrbuch der Zootomie, of which only the vertebrate section was corrected by himself. The precision of his earlier work is evidenced by his
Micrometric Measurements of the Elementary Parts of Man and Animals (Leipzig, 1834). His zoological labours may be said to conclude with the atlas
Icones zootomicae (Leipzig, 1841). In 1835, he communicated to the Munich academy of sciences his researches on the physiology of generation and development, including the famous discovery of the germinal vesicle of the human
ovum. These were republished under the title
Prodromus historiae generationis hominis atque animalium (Leipzig, 1836). As in zoology, his original researches in physiology were followed by a students' textbook,
Lehrbuch der speciellen Physiologie (Leipzig, 1838), which soon reached a third edition, and was translated into French and English. This was supplemented by an atlas,
Icones physiologicae (Leipzig, 1839). To the same period belongs a very interesting (but now little-known) work on medicine proper, of a historical and synthetic scope:
Grundriss der Encyklopädie und Methodologie der medicinischen Wissenschaften nach geschichtlicher Ansicht (Erlangen, 1838). It was translated into
Danish. About the same time he worked at a translation of
James Cowles Prichard's
Natural History of Man, and edited various writings of
Samuel Thomas Sommerring, with a biography of that anatomist (1844), which he himself fancied most of all his writings. In 1843, after his removal to Göttingen, he began his great
Handwörterbuch der Physiologie mit Rücksicht auf physiologische Pathologie123.13.24, and brought out the fifth (supplementary) volume in 1852. His only original contributions to this work were on the sympathetic nerve, nerve-ganglia and nerve-endings, and he modestly disclaimed all merit except as being the organizer. While resident in Italy for his health from 1845 to 1847, he occupied himself with research on the electrical organ of the
torpedo genus of electric eels and on nervous organization generally; these he published in 1853–1854 (
Neurologische Untersuchungen, Göttingen), and therewith his physiological period may be said to end. ==Philosophy==