198 NORMAL HISTOLOGY. 



of a substance, called "eleidin," within the cytoplasm (Fig. 175). 

 These cells form the " stratum granulosum." The eleidin appears 

 to be produced at the expense of the cytoplasm, the process being 

 a form of degeneration, so that after a while the whole cell is con- 

 verted into a homogeneous material in which the nucleus persists 

 in a form deprived of chromatin, and therefore insusceptible of 

 staining. The presence of these cells gives rise to the formation of 

 the "stratum lucidum" immediately above the stratum granules urn. 

 Within this stratum the eleidin appears to pass into a closely related 

 substance of a horny nature, keratin, and the cells become con- 



FIG. 175. 



Cell from the stratum granulosum of the epidermis of the scalp. (Rabl.) The cytoplasm of 

 the cell has been in great measure converted into granules of eleidin ; the chromatin of 

 the nucleus has retracted into a compact mass in the centre of the nuclear region, and is 

 destined to disappear. This cell is from a section made parallel to the surface of the 

 epidermis, which accounts for its shape and apparent size. 



verted into firmly compacted scales, which make up the most super- 

 ficial or horny layer of the epidermis. 



The sweat-glands are simple tubular glands, the deep ends of 

 which are irregularly coiled to form a globular mass situated in 

 the deeper portion of the corium or at various depths in the sub- 

 cutaneous tissue. From these coils the excretory duct passes 

 through the corium to the epidermis, where it opens into a spiral 

 channel between the epidermal cells, ending in an orifice at the sur- 

 face of the skin. 



The epithelial lining of the sweat-gland is a continuation of the 

 stratum mucosum, from which it is derived, and consists of two or 

 more layers of cubical cells in the duct and of a single layer of more 

 columnar cells in the deeper, secreting portion of the gland. In 

 the duct these cells rest upon a homogeneous basement-membrane, 

 but in the secreting portion there is a more or less complete layer 

 of elongated cells, similar in appearance to those of smooth muscular 

 tissue, which lie between the epithelial cells and the basement-mem- 

 brane (Fig. 176). It is doubtful whether these are really muscle- 

 cells. The loops of the glandular coil are surrounded by fibrous 

 tissue, which contains the bloodvessels supplied to the gland and 

 serves to support it in its globular form. 



