1138 GENERAL ANATOMY OR HISTOLOGY. 



connecting adjacent cells. Between the cells are fine intercellular clefts, which 

 serve for the passage of lymph and in which lymph-corpuscles or pigment granules 

 may be found. (2) Immediately superficial to these are two or three layers of 

 flattened, spindle-shaped cells, the stratum granulosum, which contain granules 

 that become deeply stained in hsematoxylin ; the granules consist of a material 

 named eleidin, an intermediate substance in the formation of horn. They are 

 supposed to be cells in a transitional stage between the protoplasmic cells of the 

 stratum Malpighii and the horny cells of the superficial layers. (3) Above this 

 layer the cells become indistinct, and appear, in sections, to form a homogeneous 

 or dimly striated membrane, composed of closely packed scales, in which traces of 

 a flattened nucleus may be found. It is called the stratum lucidum. (4) As these 

 cells successively approach the surface by the development of fresh layers from 

 beneath, they assume a flattened form from the evaporation of their fluid contents, 

 and consist of many layers of horny epithelial scales in which no nucleus is 

 discernible, forming the stratum corneum. These cells are unaffected by acetic 

 acid, the protoplasm having become changed into horny material or keratin. Ac- 

 cording to Ranvier, they contain granules of a material which has the characters 

 of beeswax. The deepest layer of the stratum Malpighii is separated from the 

 papillae by an apparently homogeneous basement membrane, which is most 

 distinctly brought into view in specimens prepared with chloride of gold. This, 

 according to Klein, is merely the deepest portion of the epithelium, and is " made 

 up of the basis of the individual cells, which have undergone a chemical and 

 morphological alteration." The black color of the skin in the negro and the 

 tawny color among some of the white races is due to the presence of pigment in 

 the cells of the cuticle. This pigment is more especially distinct in the cells of 

 the deeper layer, or stratum Malpighii, and is similar to that found in the cells of 

 the pigmentary layer of the retina. As the cells approach the surface and desic- 

 cate, the color becomes partially lost ; the disappearance of the pigment from the 

 superficial layers of the epidermis is, however, difficult to explain. 



The derma, corium, or cutis vera, is tough, flexible, and highly elastic, in order 

 to defend the parts beneath from violence. 



It varies in thickness, from a quarter of a line to a line and a half, in different 

 parts of the body. Thus it is very thick in the palms of the hands and soles of 

 the feet; thicker on the posterior aspect of the body than the, front, and on the 

 outer than the inner side of the limbs. In the eyelids, scrotum, and penis it is 

 exceedingly thin and delicate. The skin is generally thicker in the male than in 

 the female, and in the adult than in the child. 



The corium consists of felted connective tissue, with a varying amount of 

 elastic fibres and numerous blood-vessels, lymphatics, and nerves. The fibro- 

 areolar tissue forms the framework of the cutis, and is differently arranged in 

 different parts, so that it is usual to describe it as consisting of two layers : the 

 deeper or reticular layer, and the superficial or papillary layer. Unstriped 

 muscular fibres are found in the superficial layers of the corium^ wherever hairs 

 are found ; and in the subcutaneous areolar tissue of the scrotum, penis, labia 

 majora of the female, and the nipples. In the latter situation the fibres are 

 arranged in bands, closely reticulated and disposed in superimposed laminae. 



^ The reticular layer consists of strong interlacing fibrous bands, composed 

 chiefly of the white variety of fibrous tissue, but containing, also, some fibres of 

 the yellow elastic tissue, which vary in amount in different parts, and connective- 

 tissue corpuscles, which are often to be found flattened against the white fibrous 

 tissue-bundles. Toward the attached surface the fasciculi are large and coarse, 

 and the areolae which are left by their interlacement are large, and occupied by 

 adipose tissue and sweat-glands. Below this the elements of the skin become 

 gradually blended with the subcutaneous areolar tissue, which, except in a few 

 situations, contains fat. Toward the free surface the fasciculi are much finer, 

 and their mode of interlacing close and intricate. 



The papillary layer is situated upon the free surface of the reticular layer ; it con- 



