Journal of comparative neurology . dingto Smith (06, p. 255): When this part of the cell is free frompigment it appears to contain a \acuole. The distribution of pigment is variable under different cir-cumstances; the limit of proximal migration in either tj-pe ofcell, however, is conditioned by the position of the nucleus(fig. C), for pigment is never found proximal to it. The lengthof the pigment cells, and therefore the thickness of the retinaas a whole, varies at different levels in the eye. The thickestportion of the retina is on the sides at a distance of about 60 m 368 LESLIE B. AREY fr
Journal of comparative neurology . dingto Smith (06, p. 255): When this part of the cell is free frompigment it appears to contain a \acuole. The distribution of pigment is variable under different cir-cumstances; the limit of proximal migration in either tj-pe ofcell, however, is conditioned by the position of the nucleus(fig. C), for pigment is never found proximal to it. The lengthof the pigment cells, and therefore the thickness of the retinaas a whole, varies at different levels in the eye. The thickestportion of the retina is on the sides at a distance of about 60 m 368 LESLIE B. AREY from the apex of the optic sac. At this thickest region, thedistance from the optic capsule to the central zone, that is, thelength of the pigment cells, is approximately 35 /x. The unpigmented or sensory cells (fig. C, nl. cl. sns.) are muchmore robust and have larger nuclei than either kind of pigmentcell just described. These cells are of an elongated spindleshape, thickest in the region of the nucleus. The cell body fbrlo. )^ pre. nt. Fig. C A portion of an axial section of a Planorbis eye, showing the com-ponent retinal elements (X 1000). ax. bac, axis of rod; cps. opt., optic capsule;fbrl., fibrillae of rod-axis;/6rZ., fibrillae of rod-mantle; ivlr. bac, mantle (in-volucrum) of rod; nl. cl. pig., nucleus of pigment cell; 7il. cl. sns., nucleus of sen-sory cell; pig., pigment; pre. nt., neurite-process of sensory cell; rtn. ex., periph-eral zone of retina; rtn. i., central zone of retina; rtn. m., middle or pigmentedzone of retina. continues through the pigment zone and ends, in the so-calledcentral zone, in a structure known as the rod—this being thephotoreceptive portion of the cell. Each rod consists of twoparts, centrally a core or axis (ax. bac), and peripherally aradially striate mantle (ivlr. bac). Proximal to the nucleus,each sensory cell gives off a neurite {pre. nH.), which coursesalong the inner face of the capsule and is ultimately gatheredup with
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Keywords: ., bookauthorw, bookcentury1900, bookdecade1910, booksubjectmedicine
