INFLUENCE OF SUNLIGHT. 41 



hardiest and strongest breeds of ponies for their size, namely 

 the Deli ponies, comes from the north of Sumatra. Although 

 climatic cold diminishes the bad effect which damp has on the 

 muscular development of horses, its good influence in this 

 respect appears to be obtained at the cost of increased suscep- 

 tibility to diseases connected with the organs of breathing. 

 Thus we succeed in breeding in England, big, powerful 

 horses ; but unfortunately many of them, Shires, Clydesdales, 

 and thoroughbreds, " make a noise," and are much more liable 

 to coughs and colds than horses which live in warm climates. 

 The bad effects of damp on horses are shown not only con- 

 stitutionally, but also in the quality and formation of the 

 animals' feet, which, when kept under its influence, become 

 weak, flat, and often diseased. The fact therefore remains 

 that the horses which have the greatest immunity from roaring 

 and other diseases of breathing, and which have the strongest 

 feet, are those that are bred and brought up in dry climates. 



INFLUENCE OF SUNLIGHT ON HORSES. 



Sunlight, to the extent which we experience it in 

 England, has a direct and an indirect influence for good on 

 the health of horses. In human beings it apparently improves 

 the quality of the blood, seemingly by its action on the red 

 corpuscles. The " sun cure " has therefore been prescribed 

 with more or less success for various diseases of mankind. 

 From experience, I think we may safely assume that sun- 

 light directly promotes the health of horses ; supposing that 

 its intensity is not tropical. Respecting its indirect action 

 as a destroyer of disease germs there can be no doubt. 

 Thus, Arloing tells us that sunlight impedes the growth of 

 the bacilli of anthrax ; Hewlett states that direct sunlight 

 destroys the bacilli of tetanus in from fifteen to eighteen 

 hours ; and Sherrington mentions that the microbes of glan- 

 ders are killed by sunlight in about three days. It is sup- 



