10 GENERAL ANATOMICAL CHARACTERS 
albinism—a condition in which the pigment or colouring matter 
usually present in the tissues constituting the external coverings of 
the body, and which gives them their characteristic hue, is absent. 
When it occurs the hair is of an opaque white, the claws, hoofs, etc., of 
a pale horn-colour, and the skin and eyes pink, in consequence of the 
colour of the blood which circulates through them being no longer 
concealed by the stronger hues of the pigments. An animal in this 
condition is called an albino. In complete albinism there is a total 
absence of pigment throughout the system. This condition occurs 
occasionally as an individual peculiarity among wild animals of 
many kinds; but it has never been perpetuated among them in dis- 
tinct races or species. The disadvantage of absence of pigment 
in the eye, causing a certain amount of intolerance of light, is 
probably sufficient to account for this. Several races of true 
albinos, as White Ferrets, Rabbits, Rats, and Mice, have, however, 
been established under the protection of man, and in them this ab- 
normal condition is propagated from generation to generation. 
Partial albinism—a condition in which the absence of pigment 
is limited to portions of the surface, or, at all events, does not extend 
to the eyes—is much more common as an individual variation both 
in domestic and in wild animals. It is possible that the artificial 
conditions incident to domestication increase the tendency to its 
occurrence ; but, whether this be so or not, it certainly becomes 
perpetuated more frequently among domesticated than among wild 
animals. This may be accounted for partly by its proving of no 
disadvantage to them, and partly by the frequent selection by man 
of animals of such colour in preference to others. The result is that 
there is no completely domestic animal of which white races do not 
exist. On the other hand, to most wild animals even partial 
albinism seems to be a disadvantage in the struggle for existence, 
since, except in the case of species inhabiting lands continually 
covered with snow, it renders them more conspicuous objects both 
to their enemies and their prey, and hence it is rarely perpetuated. 
In northern regions, however, a large proportion of species are 
regularly and normally of a white colour, either, as the Polar Bear, 
all the year through, or, as the Ermine or Stoat, Arctic Fox, and 
Alpine Hare, during the winter season. The coloration in these 
cases is obviously protective, as it is also to a great extent in many 
other instances throughout the class. 
Among conspicuously coloured mammals, it has been observed 
that the vertical black and tawny stripes of the Tiger harmonise so 
well with the brown and green grasses of its native jungle as to 
render the animal almost invisible when lying among them ; while 
the dappled hide of the Giraffe is said to agree equally well 
with the chequered splashes of light and shade in the clumps of tall 
mimosas among which it feeds) The uniformly tawny hue of the 
