SUDORIPAROUS GLANDS 205 



cial strata of spheroidal vesicular cells. The latter are known as 

 the stratum intermedium. By the fifth or sixth month cell differ- 

 entiation has advanced in the intermediate portion until cornifi- 

 cation can be distinguished in its superficial cells. 



Further development is analogous to the growth of the mature 

 epidermis; new cells are rapidly formed in the deeper portion, 

 stratum germinativum, and are steadily pushed toward the surface, 

 their migration being either accompanied by slight, or later by 

 more pronounced cornification, which in the latter case gives rise 

 to the stratum granulosum, stratum lucidum, and horny layer, but 

 in the former produces only relatively slight flattening of the 

 superficial cells without the appearance of keratin or the disap- 

 pearance of the nucleus. 



The derma arises from the superficial layers of the mesoblast 

 as ordinary connective tissue, in which the appendages of the skin 

 make their appearance as ingrowths from the epidermis. Certain 

 mesenchymal cells form the smooth muscle fibres of the arrector 

 pili muscles and of the derma of those locations where muscle is 

 present in the mature skin. Other mesenchymal cells produce 

 the fat lobules of the subcutaneous tissue. Papillae appear during 

 the fourth or fifth month but do not attain their completed devel- 

 opment until much later. 



The CUTANEOUS APPENDAGES include the sudoriparous 

 glands, the nails, the hairs, and the sebaceous glands. 



SUDORIPAROUS GLANDS (the Coil Glands, Sweat Glands). 

 The sudoriparous glands occur in all portions of the skin, but 

 more abundantly in certain locations, e. g., palms of the hands, 

 soles of the feet, axillae, groin, and circumanal region. They are 

 long, coiled or convoluted, tubular glands whose secreting portions 

 lie in the subcutaneous tissue and in the deeper part of the 

 corium ; their ducts extend through the corium to the under sur- 

 face of the epidermis where the lining epithelium of the duct 

 becomes continuous with the cells of the interpapillary portion of 

 the stratum germinativum. In its further course through the epi- 

 dermis the duct of the gland forms only a tortuous spiral cleft or 

 passage whose wall is formed only by the concentrically placed 

 cells of the various epidermal layers through which it passes. 



The secreting or coiled portion of the gland (fundus) consists 

 of a delicate hyaline membrana propria in whose outer portion are 

 concentrically disposed connective tissue fibres. The inner por- 



