io 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 



