148 SKIN AND ITS APPENDAGES. 



of termination of the cutaneous nerves (PL XIV 



%. ii). 



lymphatics. The lymphatics of the skin form a very close web in 

 the papillary layer, communicating by larger branches 

 with the subcutaneous vessels of the same system. 

 We possess no positive information as to their mode 

 of origin. M. Kiiss asserts that they are in direct 

 communication with the deep stratum of the epi- 

 dermis. 



The cutaneous glands have been already described. 

 Development. According to Bischoff, the skin can be distinguished 

 as a distinct membrane as early as the commence- 

 ment of the second month of foetal life. The true 

 skin, as yet consisting entirely of embryonic cells, 

 very soon acquires an increased degree of density, 

 and becomes distinct from the epidermis ; later, the 

 cells are metamorphosed, some of them into connec- 

 tive and elastic fibres, and others into vessels, etc. 

 Finally, a certain proportion of them seem to undergo 

 a temporary arrest in their development, and consti- 

 tute what have been denominated plasrnatic cells. 

 As for the epidermis, it is developed by the multi- 

 plication and increase in volume of its globular ele- 

 ments. Although the fact has not as yet been 

 demonstrated, it is probable that this multiplication 

 of cells is effected, both in the embryo, and through- 

 out life, by the endogenous generation of new nuclei, 

 and subsequent cleavage of the parent cell. 



Preparation. To study its structure, very thin sections both of 

 recent and dried skin, must be made by a razor. 

 Acetic acid renders these sections more transparent, 

 and caustic potash has the same effect, but breaks 



