VITIATION OF THE SYSTEM. 25 



blood is not completed. Notwithstanding this, however, 

 Spanish and Arabian horses, though small, are remarkable 

 for strength and agility. We account for this difference in 

 effect by referring to opposite causes; the watery parts of 

 the blood being abstracted through the skin and lungs, it 

 becomes thicker and more exciting; hence vegetables in 

 those climates are more nutritive than watery. 



Warm and moist rarified air, also mingled with watery 

 particles, is rendered light, pleasant, and little exciting. 

 Heat dilates, and weakens the tissues; humidity lessens 

 the transpirations, and renders change of the blood incom- 

 plete, producing a less arterial fluid. Moreover, the plants 

 growing in these places, are large, luxurious, porous, aqueous, 

 and furnish but little nutriment. Animals bred in such 

 climates, in marshes, near pools, in the vicinity of stagnant 

 water, have abundant cellular membrane, a very large amount 

 of venous blood, a muscular system wanting energy, a re- 

 spiration short and quick, the hearths pulsations scarcely 

 perceptible, and are disposed to fatten, also to catarrhal 

 diseases, discharges, &c. Moreover, the aqueous vapour of 

 this air is seldom pure ; produced from stagnant waters, it 

 frequently contains emanations from decaying vegetable and 

 animal matter, from which arise the carburet, phosphoret, 

 and the compounds of, hydrogen — gases which are pre- 

 judicial to life in every form, and cannot be inhaled with 

 impunity. These are introduced through the breath and 

 with the water drank, engendering putrid typhoid and car- 

 bunculous disorders. The warm and humid air of stables, 

 especially in winter, creates the same dispositions, followed 

 by the same effects. Sometimes it happens that this un- 

 wholesome air causes sudden determinations of blood to the 

 spleen, lungs, brain, or intestines ; at other times, it pre- 

 disposes the confined animals to catarrh, to chronic pneu- 

 monia, and to mange. 



- Air, cold and moist j that which is indicated by the pre- 

 valence of hoar frost and by ice coating the window-panes. 

 Air impregnated with moisture, forms a suitable vapour 

 bath, in which animals are kept constantly plunged. Such 



