On Mismanagement of Farm-Horses. 



531 



a more rapid combustion is necessary to maintain the heat of the 

 body, and a larger quantity of fuel must be supplied to support 

 that combustion. The cooling of the body," says Liebig, " by 

 whatever cause it may be produced, increases the amount of food 

 necessary." * Sheep exposed to the inclemency of winter 

 weather eat much larger quantities of food and fatten more slowly 

 than those in sheltered situations and receiving the same sort of 

 food. The milk yielded by cows is often much diminished if 

 the animals are exposed to cold, even for a short while. Indeed, 

 amongst all animals, the effects of cold are greatly aggravated by 

 insufficient food. Their conjoined influence on man is thus 

 clearly stated by Sir John Richardson : — During the whole of 

 our march we experienced that no quantity of clothing could 

 keep us warm while we fasted ; but on those occasions on which 

 we were enabled to go to bed with full stomachs we passed the 

 night in a warm and comfortable manner." j 



When air at low temperatures is set in motion, as by winds, the 

 sensation of cold becomes much aggravated, and sometimes almost 

 unbearable. In such cases, however, there is no diminution in 

 the temperature of the air. During the keen piercing winds 

 which occasionally sweep over our island, the thermometer indi- 

 cates that degree of temperature which, in the absence of these 

 winds, would be considered mild and agreeable. This influence 

 of winds, in aggravating the effects of cold, has been noticed by 

 most Arctic voyagers. Thus it is stated by Parry, that he and 

 his crew suffered more from cold in a breeze with the thermo- 

 meters at 32^ Fahr. than in calm weather with the thermometers 

 at zero. The explanation of this is very obvious. Cold air in 

 motion causes more rapid evaporation of fluid from the skin than 

 air at rest of the same temperature ; for it speedily displaces the 

 atmosphere of warm humid air which surrounds the body, and 

 substitutes instead fresh quantities of air at a lower temperature, 

 and hence possessed of greater heat-abstracting power. In this 

 way we may in part account for the great consumption of food, 

 the tardy growth, and poor condition of badly-sheltered horses. 



But insufficient shelter, besides exposing horses to the evils of 

 cold, also affords them imperfect protection against undue mois- 

 ture. The inhalation, for any considerable length of time, of an 

 atmosphere surcharged with moisture, cannot but exercise a dele- 

 terious influence on the animal body ; for such an atmosphere 

 contains, in proportion to its volume, less oxygen than drier air, 

 and possesses a power of diffusion considerably inferior to it. 

 This diminished power of diffusion interferes with the full and 

 rapid arterialization of the blood — a process on the due activity 



* Familiar Letters on Chemistry, p. 73. 



t Franklin's Journey to the Polar Seas, vol. i. p. 421. 



2 M 2 



