Jeffries.} 206 [February 7, 



abundant capillary systems for the blood and lymph, which 

 extend out to the mucous layer and supply it with food. Pig- 

 ment, when found in parts of the skin not specially modified, is 

 limited to the cutis vera, there being a bed of small pigment 

 cells (fig. 1 d) directly below the mucous layer and large 

 masses of pigment in the deeper parts of the cutis vera. 



DEVELOPMENT OF THE EPIDEEM. 



The epiderm, which is the representative of the epiblast of the 

 embryo, is formed during the earlier hours of incubation in a 

 way not necessary to describe. About the second day of incu- 

 bation the epiblast becomes roughly two-layered. At first both 

 of these layers consist of roundish cells with conspicuous nuclei 

 and nucleoli embedded in an intercellular substance. The outer 

 cells, however, shortly become flattened out into a layer of poly- 

 gonal cells, thus forming the epitrichial layer of German authors. 

 This layer is usually distinct by the fifth day, from which time 

 the growth of the skin may be said to date. 



During the middle of the fifth day the mucous layer consists 

 of large cuboidal cells (fig. 2 b) of about .01 mm., with a large 

 nucleolus .004 m.m., — with one or more dark nucleoli. Contrary 

 to the observations of Frommann the cells of the mucous layer 

 seem to be distinct and not to form a uniform mass or symcit- 

 sium. The basal walls 1 of the cells are distinct and rather thick, 

 while the walls between the different cells are thickened at the 

 base and gradually thin out towards the top of the cells. The 

 walls of the top, or outer surface, are very indistinct and often not 

 to be seen ; a natural result of all the outer cells being cut off 

 from the outer ends of the mucous cells. The cell walls or inter- 

 cellular substance is easily stained with a few drops of a strong 

 alcoholic solution of eosin dropped into true benzole, or by 

 nitrate of silver, — the first method however is the easier and 

 more permanent. 



The epitrichial layer (fig. 2 a) though perfectly distinct, is in 

 a very elementary condition. It consists of cells, in nature like 

 those of the mucous layer, more or less flattened into discs, 

 dispersed through a mass of intercellular substance. The nuclei 



1 This word is used to represent the parts which act as walls, even if composed of 

 intercellular substance. 



