320 MICROSCOPIC ANATOMY OF THE ORGANS. 



In the corium we find in certain places (e. g., in the face) 

 striated muscle fibres, extending up to the pars papillaris. 

 There occur also smooth muscle cells, which run in bundles 

 parallel to the surface and form special networks in the skin 

 of the scrotum (tunica dartos) and the nipple. The smooth 

 muscles of sweat glands and those which are connected with 

 hairs will be spoken of later. 



The subcutaneous tissue (tela subcutanea) which joins the 

 skin to the neighboring parts is made up of interlacing con- 

 nective-tissue strands, in the meshes of which fat is found 

 (Fig. 241). When the fat reaches a considerable development, 

 this layer is spoken of as the panniculus adiposus. In a few 

 exceptional instances the fat is entirely wanting in the sub- 

 cutaneous tissue (e. g., in the outer ear, the scrotum, etc.). The 

 more horizontal i. e., parallel to the surface of the skin the 

 connective-tissue bundles run, the longer they are and the 

 greater is the movability of the skin. The wrinkling of the 

 skin is dependent on the length of these bundles. If they are 

 short, they run more nearly at right angles to the surface 

 of the skin, and the latter cannot be moved or thrown into 

 folds. 



At the boundary between the corium and the epidermis we 

 find a very thin structureless membrane, the so-called basal 

 membrane. 



The epidermis is composed of a many-layered epithelium. 

 Two parts in this may be distinguished : the outer one, which 

 consists of corneous cells (horny layer, stratum corneum), and 

 the deeper-lying part, the so-called Malpighian layer (stratum 

 Malpighii, stratum gerrninativum). The latter may again be 

 divided into many layers, which, spoken of from below up, are 

 the stratum cylindricum, stratum spinosum, stratum granulosum, 

 and stratum lucidum (Fig. 244). 



The degree of development of the horny layer and the 

 Malpighian layer differs in various parts of the body. Usually 

 the latter is the thicker of the two, but in the vola manus 

 and the phmta |>c<lis the horny layer is greatly thickened. The 

 two lower layers of the stratum Malpighii consist of prickle 



