328 PHYSIOLOGY CHAP. 



negro and Melanesian races ; very dark brown and coal black, 

 as in various negro races. 



Anthropologists, in order to avoid misunderstanding in the 

 indication of the colour of the skin of the different races, make 

 use of a colour scale in which the various gradations are dis- 

 tinguished by means of numbers. Of these shade cards, Broca's, 

 which shows 34 gradations, is the best and the one almost uni- 

 versally adopted. 



It is nevertheless by no means difficult to make mistakes 

 when judging the natural colour of the skin. Many uncivilised 

 races are in the habit of imparting an artificial colour to the skin ; 

 this artificial colouring is sometimes connected with the process 

 of tattooing, sometimes quite independent of it. The first 

 European explorers who saw American Indians described them 

 as copper coloured ; this colouring proved, however, to be artificial 

 and to result from the custom of the Indian braves of smearing 

 the skin with a red dye before starting on any warlike enterprise. 

 The natural colour of the skin of the natives of Melanesia is 

 suffused with pink or brown owing to their habit of rubbing red 

 earth or soot into the skin ; a bronze hue may be imparted to 

 the skin by a more or less thick layer of dirt which is never 

 removed, as in the case of the natives of Tierra del Fuego. A 

 prolonged sojourn in dark places far removed from the action of 

 the solar rays will gradually reduce and attenuate the dark 

 pigment in the skin of coloured peoples, as may be seen amongst 

 the adherents of a male sect existing amongst the inhabitants of 

 New Mecklenburgh, whose rule obliges them to live for months 

 together during the daytime in low dark huts, which they are 

 only allowed to leave at nightfall (Schlaginhaufen). 



A special characteristic of the Mongolian races is the so-called 

 blue mark on infants, first noticed by Balz in 1883 on Japanese 

 children. This cutaneous mark is grey-blue in colour, round or 

 oval in form, with a diameter of from 0'5 to 5 cm. and is situated 

 above the coccyx ; it disappears during childhood. It occurs 

 most frequently amongst Mongolians, of whom 80-90 per cent 

 have it, but is also seen on children of other coloured races (Ainu, 

 Samoan, Negro, Indian) ; in these cases, however, it is blackish in 

 colour ; it is also very occasionally seen on European children of 

 non-Mongolian races (0*04- - 05 per cent according to different 

 observers). 



Three fundamental grades of colouring prevail in the iris: 

 light (blue- or grey) ; dark (light or dark brown and black) ; 

 intermediate (green, yellow, yellowish grey, etc.). Light eyes, 

 blue or grey, are to be seen only amongst the lair European races, 

 possibly also amongst Turco-Finnish peoples ; certain Mongolian 

 races have light brown eyes, all others dark brown or black. 



There are four main gradations in the colour of hair : black, 



