. Annual report of the Board of Regents of the Smithsonian Institution. Smithsonian Institution; Smithsonian Institution. Archives; Discoveries in science. 496 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1907. find in the whales and sea-cows—two widely separated stocks—a horizontal caudal fin, rudimentary hind limbs, fin-shaped fore limbs, a more or less naked skin, etc. Let us, however, look more closely at one of these structures which appear so similar. The flipper of a marine mammal is always much broader than the fore limb of a land mammal. The fin must be broad if it is to serve as a good ste
. Annual report of the Board of Regents of the Smithsonian Institution. Smithsonian Institution; Smithsonian Institution. Archives; Discoveries in science. 496 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1907. find in the whales and sea-cows—two widely separated stocks—a horizontal caudal fin, rudimentary hind limbs, fin-shaped fore limbs, a more or less naked skin, etc. Let us, however, look more closely at one of these structures which appear so similar. The flipper of a marine mammal is always much broader than the fore limb of a land mammal. The fin must be broad if it is to serve as a good steering apparatus. In the whales the broadening of the fin is accomplished by the broadening of both lower arm bones, so that the bones themselves are increased in breadth antero-posteriorly. The space between the radius and ulna is small. (Fig. 27, I.) In the sea-cows, on the contrary, the broadening of the fin results from the increased space between the radius and ulna. The radius is bent forward strongly, while the bones maintain nearly their original size. (Fig. 27, II.) In the seals, finally, the same result is reached. ,^„ „^-p. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Smithsonian Institution. Board of Regents; United States National Museum. Report of the U. S. National Museum; Smithsonian Institution. Report of the Secretary. Washington : Smithsonian Institution
Size: 1429px × 1748px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorsmithsonianinstitutio, bookcentury1800, bookdecade1840
