Jaeger, Georg Friedrich

(b.25 December 1785, Stuttgart, Germany; d. 10 September 1866, Stuttgart)

paleontogy, medicine.

The youngest son of Christian Friedrich Jaeger, a court physician, Jaeger attended the Stuttgart Gymnasium, studied medicine at Tübingen (M.D., 1808), and then spent a year traveling, during which he studied osteology and fossil skeletons under Georges Cuvier at Paris. He returned to Stuttgart and established a successful medical practice, becoming a member and eventually senior councillor of the Medicinal Collegium.¹ From 1817 until 1856 he held the post of inspector of the royal natural history cabinet,² and from 1822 until 1842 was also professor of chemistry and natural history in the Stuttgart Obergymnasium. A large man of robust health, he married twice³ and had thirteen children.

Jaeger wrote on abnormal growth and anatomy of man and animals, physiological effects of poisons on plants, parasitism, mammalian systematics and distribution, geology, and anthropology. His principal contributions were to paleontology.

In 1822 he discovered in the collections of the Stuttgart Gymnasium a slab of limestone containing a large reptile skeleton, and within this skeleton a much smaller one,⁴ Although it was unlike any reptile described by Cuvier,⁵ Jaeger recognized its smililarity to the fossil remains recently described in England and named Ichthyosaurus. His monography contains careful observations (Considering the unexposed condition of the fossil) and judicious inferences. He pointed out that the structure of the limbs is more like the paddles of a porpoise than the feet of either salamanders or crocodies, the animals between which it had been placed in classifications. In 1842 and 1852 he suggested that the ichthyosaurs may have given birth to living young.

Jaeger’s monograph on fossil plants of the Triassic sandstones near Stuttgart (1827) was followed in 1828 by a more extensive study of fossil reptiles, which contains the earliest descriptions of labyrinthodont amphibians and of the crocodile-like phytosaurs of the Triassic. He then turned his attention to the fossil mammals from fissures in the Schwabian Alb, in Germany, and in 1835 and 1839 provided the first detailed account of this material. This account was important for Jaeger’s recognition of considerable differences between the faunas of different localities. In the absence of any super-positional relationships between fissures, he failed to grasp the implication of these differences for the relative ages of the faunas; instead he sought to explain them by varying circumstances of deposition and accumulation of the bones. Although he attempted to fit them into the Cuvierian concept of an ancient fauna (that of the Paris gypsum) and a more recent assemblage of still living animals mixed with not long extinct species such as were found in caves and river alluvium, he repeatedly expressed doubts about this interpretation, and arranged the various faunas in their proper time sequence. He also described the tusks of mammoths and associated fossils found near Stuttgart in 1700 and 1816.⁶ In addition to these monographs Jaeger wrote many shorter articles on various vertebrate fossils.

Jaeger actively promoted science, medicine, and natural history. He was highly regarded by his contemporaries, a member of thirty-five academies and learned societies, and a recipient of state and national honors.

NOTES

1. The highest health authority in Wüurttemberg.

2. His brother, Carl Christian Friedrich Jaeger, had held this post from 1798-1817.

3. Jaeger married Charlotte Hoffmann, who died in 1818, leaving two sons and two daughters. He later married Charlotte Schwab, who bore four sons and five daughters.

4. These specimens, from Boll, in Wüurttemberg, had been collected in 1749 by Christain Albert Mohr and described as fishes in an unpublished dissertation. Boll had been known as an important locality for fossils since the 1598 memoir of J. Bauhim.

5. Recherches sur les ossemens fossiles de quadrupedes, ou l’on retablit les caracteres de plusieurs especes d’animaux que les revolutions du globe paroissent avoir detruites, 4 vols. (Paris, 1812); later eds. include a section on ichthyosaurs.

6. The caches of mammoth ivory at Cannstatt, near Stuttgart, attracted great attention. Those found in 1700 were largely sold for medicine; a piece of “unicorn horn” from this find was given by Duke Eberhard Ludwig of Wüurttemberg to the citizens of Zurich to help them fight a plague epidemic. King Frederick I of Wüurttemberg personally supervised the excavations in the winter of 1816-1817; and he died of pneumonia contracted during this work.

BIBLIOGRAPHY

I. Original Works. Jaeger’s works include De effectibus Arsenici albi in various organismos (Tübingen, 1808), dissertation; Anleitung zur Gebirgskunde (Stuttgart, 1811); Über die Missbildungen der Gewächse (Stuttgart, 1814); Das wissenwürdogste aus der Gebirgskunde (Stuttgart, 1815); De Ichthyosauri sive proteosauri fossilis speciminibus in agro Bollensis in Wüurtembergia repertis commentatur Georgius Friendericus Jaeger (Stuttgart, 1824); Ueber die Pflanzenversteinerungen des Bausandsteins in Stuttgart (Stuttgart, 1827); Über die fossilen Reptilien, welche in Wüurttemberg aufgefunden worden sind (Stuttgart, 1828); Über die fossilen Säugethiere, welche in Württemberg aufgefunden worden sind (Stuttgart, 1835), continued as üuber die fossilen Säugethiere, welche in Württemberg in verschiedenen Formationen aufgefunden worden sind, nebst geognostischen Bemerkungen über diese Formationen (Stuttgart, 1839); Beobachtungen und Untersuchungen üuber die regelmäassigen Formen der Gebirgsarten (Stuttgart, 1846); and Ueber die Wirkung des Arseniks auf Pflanzen in Zusammenhang mit Physiologie, Landwirtschaft und Medicinalpolizei (Stuttgart, 1864).

II. Secondary Literature. Citations of Jaeger’s publications dealing with fossil vertebrates are given in A. S. Romer et al., “Bibliography of Fossil Vertebrates Exclusive of North America 15099—1927,” in Memoirs of the Geological Society of America, 87 (1962), II, 685-687 (contains 44 titles). J. G. von Kurr lists 28 articles dealing with natural history, including the major paleontological monographs, in Württembergische naturwissenschaftliche Jahreshefte, 23 (1867), 34-36; 27 short papers are noted in the index, 20 (1864), 315-16. A Hirsch lists a few medical papers in Biographisches Lexikon der hervorragenden Ätrzte aller Zeiten und Völker, III (Vienna-Leipzig, 1886), 372-373.

Biographical notices have been published by C. G. Carus in Leopoldina, 5 (1866), 138; and J. G. von Kurr (see above), who says that Jaeger published 143 articles, presumably about half of which were on medical subjects. For an appreciation of Jaeger’s paleontological work see K. Staesche, “Ein Jahrhundert Paläontologie in Württemberg,” in Jahresheft des Vereins für vaterländische Naturkunde in Württemberg, 113 (1958), 24.

Joseph T. Gregory