8o .PERSONAL APPEARANCES IN HEALTH AND DISEASE. 



be at work, but we can hardly invoke here the hypothesis 

 that derangement of hepatic function, gravely as this 

 is affected by heat, has anything to do with it, seeing 

 that the result is only shown upon those parts of the skin 

 which are exposed to the air. The influence of light in 

 this connexion should not be lost sight of; for those 

 who work in dark places are pallid, just as plants kept in 

 the dark are ; and though we may not be able to explain 

 the modus operandi, yet we must think that light has 

 some effect. Fair skins are especially liable to pigmenta- 

 tion from exposure to air and light, as is seen in the 

 production of " freckles " or " sun-spots " on the face and 

 neck, and hands. These are nothing more than limited 

 collections of pigment, and as is well known they often 

 disappear when youth is passed. 



CHAPTER IX. 



CHANGES IN COLOUR IN HEALTH. 



HITHERTO we have spoken only of changes in colour due 

 to alterations in the amount of pigment in different 

 regions of the body. Many of those changes are of but 

 slight importance, for depending upon local influences 

 they have no direct relation to the general health of the 

 individual. It is far otherwise with the colour changes 

 we have now to deal with; foj although, as we have 



