ITS STRUCTURE AND FUNCTIONS. 261 



knuckle, after it has stopped bleeding, for you must all have 

 noticed how a pale yellow clear liquid oozes then from the sore 

 place, and soon forms a scab or protection to the wound, enabling 

 the process of repair to be carried on. In the dermis, also, we 

 nmst not forget the nerves, with their curious nerve-endings, very 

 varied in form, and constituting the sense-organs of touch. They 

 are frequently small oval bodies, like little seeds, situated on the 

 nerve fibres. 



As we proceed to the deeper parts of the dermis, the fibrous 

 tissue becomes less dense, and, at a certain depth below the sur- 

 face, we find little dark bodies — very well shown in the sections — 

 the sweat-glands. As these have such important functions to 

 perform, I must ask' your permission to dwell on them briefly. 



Let us ask, in the first place, what is a gland ? It is an organ 

 which has for its functions the manufacture of some fluid which 

 has a definite composition and definite action. In its simplest, or 

 its most elaborate form, it is nothing more than a single row of epi- 

 thelial cells, lying on a basement membrane, with blood-vessels 

 underneath, the cells being free to the surface at their opposite side. 



jTQIEEmia^c 



D 



Fig. 65 — ^Simple secreting surface, or Mucous Membrane. A, Free 

 surface ; B, Epithelial Cells ; C, Basement Membrane ; Z?. Fibrous 

 coat ; £,I^, Blood-vessels. 



These epithelial cells pick out material they want from the 

 blood circulating below them. They eat these, and, in the eating 

 of them, manufacture certain new materials, which they pour out 

 on to the open surface in the form of a liquid, called the Secretion 

 of the particular gland in question, e.g., the Saliva, Gastric Juice, 

 Bile, Sweat, etc. Thus, the sweat is the secretion or product of 

 the activity of the epithelial cells of the skin ; but in our highly 

 elaborated bodies instead of all the epithelial cells having this 

 function, it has been especially relegated to certain portions of 

 them, and they, instead of lying flat on the surface, dip down into 

 the skin, and there coil about so as to increase many times the 



