File:Elements of physiological psychology; a treatise of the activities and nature of the mind, from the physical and experimental points of view (1911) (14773781615).jpg

Identifier: cu31924003161761 (find matches)
Title: Elements of physiological psychology; a treatise of the activities and nature of the mind, from the physical and experimental points of view
Year: 1911 (1910s)
Authors: Ladd, George Trumbull, 1842-1921 Woodworth, Robert Sessions, joint author
Subjects: Psychophysiology
Publisher: New York, C. Scribner's sons
Contributing Library: Cornell University Library
Digitizing Sponsor: MSN

View Book Page: Book Viewer
About This Book: Catalog Entry
View All Images: All Images From Book
Click here to view book online to see this illustration in context in a browseable online version of this book.

Text Appearing Before Image:
the two elements is different for different parts ofthe retina. In the yellow spot only cones appear, but these are ofmore slender form, and of increased length, so that not less than onemillion are supposed to be set in a square -^ inch; while not far fromthis spot each cone is surrounded by a crown-shaped border ofrods. Toward the ora serrata the cones become continually rarer.In close connection with the rods and cones stand the cells of thepigment-epithelium. These cells form a regular mosaic of flat,six-sided cells, which send out pigmented processes between theouter limbs of the rods and cones (see Figs. 81 and 82). § 21. Two minute portions of the inner surface of the retina re-quire to be distinguished from the rest of its area: the yellow spot(macida lutea) and the blind spot (papilla optica). The yellowspot is of oval shape, about t^ of an inch in its long diameter, andhas in the centre a depression called the fovea centralis. It is the 194 END-ORGANS OF THE NERVOUS SYSTEM
Text Appearing After Image:
^°So^^ Figs. 81 and 82.—Superficial Aspect of the Ar-rangement of the Rods and Cones in the Ret-ina, ^f-. (Schultze.) The former is fromthe region of the macula lutea; the latterfrom the peripheral region. place of clearest vision, and the physiological centre of the eye.About ^ of an inch inside the eye, or 15,° from the middle of theyellow spot, is the middle of the papilla, or place where the opticnerve breaks into the retina (compare Fig. 83). The blind spot, or portion of the retina whichcan be experimentally shownto be inoperative in vision,has been proved by Helm-holtz to correspond in bothsize and shape to that coveredby this papilla. Its diameteris about ^ or tV of an inch,varying considerably for dif-ferent eyes. It is wanting inall the nervous elements, ex-cept, of course, thenerve-fibres.§ 22. In answer to the question. What elements of the retina aredirectly affected by the light ? both anatomy and physiology refer tothe layer of rods and cones. This layer alone poss

Note About Images