Quain's elements of anatomy . forms the external layer of the retina of the eye, andcovers the posterior surface of the iris. Dark pigment is also met with in Fig. 78. Fig. 78.^Ramified cells, from the tissue of the CHOROID COAT OF THE EYE ; MAGNIFIED 350 DIAMETERS (Kolliker).a, cells with pigment; &, colourless fusiform cells. the deeper layers of the cuticle, especially in thecoloured races, and in certain epithelial cells ofthe membranous labyrinth of the ear, and theolfactory region of the nose (combined in thelatter case with brownish yellow pigment). In the connective tissue the pigment
Quain's elements of anatomy . forms the external layer of the retina of the eye, andcovers the posterior surface of the iris. Dark pigment is also met with in Fig. 78. Fig. 78.^Ramified cells, from the tissue of the CHOROID COAT OF THE EYE ; MAGNIFIED 350 DIAMETERS (Kolliker).a, cells with pigment; &, colourless fusiform cells. the deeper layers of the cuticle, especially in thecoloured races, and in certain epithelial cells ofthe membranous labyrinth of the ear, and theolfactory region of the nose (combined in thelatter case with brownish yellow pigment). In the connective tissue the pigment is met within enlarged and irregularly branched corpuscleswhich are termed pigment-cells. Such ramifiedcells are very common in many animals. In thehuman body cells of this description are found inthe dark tissue on the outer surface of the choroid coat, (fig. 78, a a), in theiris, where they are often variously coloured, and on the pia mater coveringthe upper part of the spinal cord. Pigment is also found in some of the. CARTILAGE. 77 ramified cells whicli form part of the retiform tissue of the medullarysubstance of lymphatic glands, and occasionally in some of the similarceUs of the spleen. It may also be seen in migratory cells, but this ismore common in pathological conditions. The pigment, strictly so called, which is contained within the cells,consists of black or brown granules or molecules of a round or oblongshape, and almost too small for exact measurement. These moleculesare densely packed together in some cells ; in others they are morescattered, and then it may be seen that there is a certain amount ofcolourless matter included along with them. When they escape fromthe ruptured cells, they exhibit very strikingly the Brownian mole-cular movement ; and in consequence of this movement the apparentfigm-e of the particles is subject to change. It is worthy of remark,that when viewed singly with a very high magnifying power they looktransparent and almost colourless, a
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