Réaumur (Fig. 29), who was distinguished for kindly and amiable personal qualities, was also an important man in his influence upon the progress of science. He was both physician and naturalist; he made experiments upon the physiology of digestion, which aided in the understanding of that process; he invented the thermometer which bears his name, and did other services for the advancement of science. [Illustration: Fig. 28.--Roesel von Rosenhof, 1705-1759.] Straus-Dürckheim's Monograph on Insect Anatomy.--Insect anatomy continued to attract a number of observers, but we must go forward into the nineteenth century before we find the subject taking a new direction and merging into its modern phase. The remarkable monograph of Straus-Dürckheim represents the next step in the development of insect anatomy toward the position that it occupies to-day. His aim is clearly indicated in the opening sentence of his preface: "Having been for a long time occupied with the study of articulated animals, I propose to publish a general work upon the comparative anatomy of that branch of the animal kingdom." He was working under the influence of Cuvier, who, some years earlier, had founded the science of comparative anatomy and whom he recognized as his great exemplar. His work is dedicated to Cuvier, and is accompanied by a letter to that great anatomist expressing his thanks for encouragement and assistance. [Illustration: Fig 29.--Réaumur, 1683-1757.] Straus-Dürckheim (1790-1865) intended that the general considerations should be the chief feature of his monograph, but they failed in this particular because, with the further developments in anatomy, including embryology and the cell-theory, his general discussions regarding the articulated animals became obsolete. The chief value of his work now lies in what he considered its secondary feature, _viz._, that of the detailed anatomy of the cockchafer, one of the common beetles of Europe. Owing to changed conditions, therefore, it takes rank with the work of Malpighi and Lyonet, as a monograph on a single form. Originally he had intended to publish a series of monographs on the structure of insects typical of the different families, but that upon the cockchafer was the only one completed.