STRUCTURE OF THE EPIDERMIS SUPERFICIAL LAYER. 229 



mucous layer, where in the normal state they are only 

 sparingly present, though they become very numerous in 

 pathological conditions (pointed condylomata, eczema, Biesia- 

 decki). 



Portions of skin that have been hardened in chromic acid or 

 Mailer's fluid are best adapted for the investigation of the 

 mucous membranes, and are at all events superior to those that 

 have been prepared in alcohol. The above-described vagrant 

 or migrating cells are only extremely rarely found in portions 

 of skin that have been removed from the dead body. They 

 are much more abundant in the young, and in those portions 

 of their skin that have a thick mucous layer. They are most 

 readily seen in irritated portions of skin, as after the application 

 of a blister, or in the part covering diseased bone, and finally in 

 osdematous skin. 



The fact that we find these cells sometimes half buried in 

 the corium, sometimes presenting all possible forms in the 

 different layers of the rete mucosum, that they augment in 

 numbers in irritated portions of skin, and that they are only 

 sparingly present in the healthy state, are all points in favour 

 of their locomotive power, especially as in other structures 

 provided with cells possessing similar characters their change 

 of position can be followed. 



The epithelial cells of the mucous layer are separable from 

 each other with difficulty either by mechanical or chemical 

 agents : and their intimate union is due, not so much to the 

 presence of any cementing substance, but to the interlocking 

 of these prickles and ribs. The isolation of the cells of this 

 layer is most easily accomplished in fragments of skin that 

 have been hardened in chromic acid, and then boiled for a con- 

 siderable period in moderately concentrated solution of potash . 

 The mucous layer then becomes entirely detached from the 

 corium, and the epidermis cells then readily fall asunder by 

 gently tapping them with a glass rod. 



THE SUPERFICIAL OR HORNY LAYER OF THE EPIDERMIS. 



The horny layer, or stratum corneum (Hornschichte), appears 

 on section as if composed of slightly sinuous fibres running 



