386 



HISTOLOGY 



The entire corium is somewhat arbitrarily subdivided into an outer 

 stratum papillare and an inner stratum reticulare (Fig. 387). These layers 

 blend with one another, but the outer portion consist of finer bundles of 

 connective tissue, more closely interwoven than those in the coarse net- 

 work characteristic of the stratum reticulare. Beneath the skin, but in- 

 separable from it, is the stratum subcutaneum, which is composed of areolar 

 tissue with large areas of fat cells; where the fat forms a continuous layer, 

 it is known as the panniculus adiposus. Finally the bundles of the stratum 

 subcutaneum connect more or less intimately with the fascia around the 

 muscles, or, in places, with the periosteum. 



The elastic fibers of the corium form evenly distributed networks, 

 which are finer in the stratum papillare and coarser in the stratum 

 reticulare. There is said to be a subepithelial network, and a layer of 



Depressions which 

 were occupied by 

 papillae. 



Ridge corresponding 



to a furrow of the 



corium. 



Portion of the duct of 

 a sweat gland. 



FIG. 389- EPIDERMIS DETACHED FROM THE DORSUM OF THE HUMAN FOOT, SEEN 



FROM THE LOWER SURFACE. Xi2o. 

 The dark epithelial network between the papilla is the rete Malpighii. 



numerous coarse fibers immediately above the general layer of fascia. 

 In old age a notable decrease in the elastic fibers has been recorded. 

 The muscle fibers of the corium are chiefly the small bundles of smooth 

 muscle attached to the sheaths of the hairs, forming the arrectores 

 pilorum. Smooth muscle is diffusely distributed in the nipple, and in the 

 scrotum it forms a layer pervaded by elastic tissue, known as the tunica 

 dartos. Striated muscle fibers derived from the muscles of expression 

 terminate in the skin of the face. The vessels and nerves of the corium 

 are described on page 399. 



Epidermis. If a piece of skin is boiled, the epidermis may be stripped 

 off, carrying the tunica propria with it; and the epidermis itself may be 

 separated into two layers. The outer layer is the stratum corneum; the 

 inner is the stratum germinativum. 



The stratum germinativum was formerly called the stratum mucosum or rete 

 Malpighii. It was first described by Malpighi who recognized its soft or "mucous" 



