PROTECTION BY COLOUR. 29 



better than dark ones, but having no exact data to offer, I 

 give the opinion merely for what it is worth. 



I have frequently noticed in hot climates, that white horses 

 which have little or no pigment in their skin (equine albinos' 

 as we might term them) bear exposure to hot sunshine 

 far worse than other kinds of horses. I may explain to 

 readers who have not made a special study of horses, that 

 the great majority of white and grey horses, and all coloured 

 horses, have black skins. I have also observed, though not 

 to such a convincing degree, that the darker a horse's 

 coat is, the better, as a rule, will he ward off the bad 

 effects of the sun. General Daumas in his book, Les 

 Chevanx du Sahara, was, I believe, the first to record this 

 supposed fact, which he states is accepted by the horsemen of 

 the Algerian desert. It appears that the presence of pigment 

 in the skin of negroes and other inhabitants of tropical 

 climates helps to protect the body, when it is exposed to 

 severe solar heat. We learn from experience that in such 

 a case, the skin of a black man, under similar conditions of 

 health, will feel colder to the touch than that of a European 

 or an American. We know that sunlight plays an essential 

 part in the formation of pigment, especially in plants ; and 

 it is significant that the colouring of tropical animals as 

 a rule is darker and more brilliant than that of Arctic 

 animals. In horses, melanotic tumours, which are charac- 

 terised by the formation of a very large amount of pigment, 

 are with few exceptions confined to grey horses, and in such 

 cases they almost always appear after the animal is at 

 least nine years old, at which age the coat begins to turn 

 white. Also, although I have no statistics to bear out the 

 assertion, I feel convinced, from personal observation, that 

 melanosis is a much more common disease among grey horses 

 in hot climates, than in cold or temperate ones. We may 

 reasonably hazard the conjecture that susceptibility to mela- 



