PERSONAL APPEARANCES IN HEALTH AND DISEASE. 75 



only concealed by the development of air or gas which 

 suddenly takes place at the roots of the hair and penetrates 

 the structure. Nor do such changed hairs always remain 

 invariably white ; as they grow, the pigment may still be 

 formed, so that the same hair may become half white and 

 half black. 



Before leaving the subject of the colouration of the skin, 

 one word must be said as to the colour of those structures 

 called the mucous membranes. Where the skin is said to 

 end that is, at the orifices of the body, at the eyelids, 

 at the ears, nose, mouth, &c. it is replaced by a mem- 

 brane which in its minute structure differs but little from 

 the skin itself. Like the skin it consists of several layers, 

 but the colour of these mucous membranes is red or 

 pinkish red, the very vascular tissue beneath showing 

 through the thin membrane. Hence it is that the lips 

 are red, and the same " vascularity " prevails throughout 

 all the canals and passages into which these orifices open. 



Finally, no description of the colour of the body would 

 be complete without reference to the colour of the eyes. 

 Of the general structure of the eyeball and its constituent 

 parts it does not concern us to speak here.* The 

 anterior part of the organ is all that/ is visible to us. We 

 see. between the eyelids, a central convex, glassy struo 



* For more ample details see the work in this series on the Eye. 



