. The biology of the frog. Frogs. THE SENSE ORGANS 331 as three varieties being distinguished (M. Schultze, van Genderen Stort). Some of these are movable, expanding. Papilla III "f optica n'l''" Fig. 92. — Inner surface of the inner half of the eye of Rana esculenta, show- ing the area centralis as a light-colored band above the papilla optica where the optic nerve enters. (After Gaupp.) in the dark until they may reach the periphery, and contract- ing under the influence of light. Ordinarily most of the cones do not reach the outer surface of the retina. The retina is marked by a t
. The biology of the frog. Frogs. THE SENSE ORGANS 331 as three varieties being distinguished (M. Schultze, van Genderen Stort). Some of these are movable, expanding. Papilla III "f optica n'l''" Fig. 92. — Inner surface of the inner half of the eye of Rana esculenta, show- ing the area centralis as a light-colored band above the papilla optica where the optic nerve enters. (After Gaupp.) in the dark until they may reach the periphery, and contract- ing under the influence of light. Ordinarily most of the cones do not reach the outer surface of the retina. The retina is marked by a thickening or papilla where the optic nerve enters. Above this papilla there extends in an antero-posterior direction a thickened portion of the retina known as the area cetitraiis, which probably marks the region of most acute vision, like the yellow spot in the eye of man. The cones are relatively more numerous in this region than in other parts (i c. : 2. 4 r. instead of i c. : 3 or 4 r., as elsewhere), and the rods are of relatively small size. The action of light upon the retina results in the produc- tion of several visible changes. In addition to the contraction. 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 Holmes, Samuel J. (Samuel Jackson), 1868-1964. New York Macmillan
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectfrogs, bookyear1916
