24 TRANSITION FROM HEALTH TO DISEASE. 



Morbid or Contagious Matter may likewise gain in- 

 troduction into the system through the alimentary canal^ 

 though \we have not much apparent reason to believe such is 

 often the case; nor are we well advised in regard to its 

 probable consequences when such is supposed to occur. A 

 horse having glanders will drop the discharge into the 

 manger, and smear it upon the rack and other parts of the 

 stable, in which situations the matter may dry and be 

 incrustedj and subsequently licked off by some other horse : 

 all this may happen ; considering, however, how much alive 

 horse-owners are to the danger of glanders, it is, I suspect, 

 not a common occurrence. 



Air is essential to the support of life. In the lungs it 

 changes venous into arterial blood ; innutritions or crude 

 blood into nutritious. It conveys from the skin certain 

 excrementitious matters. By pressure it maintains the 

 equilibrium of the circulating fluids, and confirms the resist- 

 ance of the solids. Its temperature and degrees of moisture 

 vary under different circumstances. The aqueous vapour it 

 contains may hold in solution different gaseous products ; 

 and in this state may predispose animals to disease. 



Cold and dry air is dense, pure, and exciting. Its effect 

 is to diminish the cutaneous and pulmonary transpiration, 

 and augment the internal functions — as change in the 

 blood, digestion, secretion, nutrition. Where the air is 

 pure, plants grow luxurious, succulent, and nutritive. The 

 moisture and temperature of the atmosphere influence the 

 forms of animals as well as their constitutions, and also affect 

 the operations of their organism. The combined action of 

 such an atmosphere with stimulating aliment produces the 

 sanguine-nervous temperament ; thence springs a predispo- 

 sition to inflammatory disease, also to nervous maladies, to 

 cerebral congestions, tetanus, and to affections of the respira- 

 tory passages in particular. 



Warm and dry rarified air is exceedingly attractive of 

 humidity. Under its influence animals mostly experience 

 great pulmonary and cutaneous transpiration ; their internal 

 secretions arc diminished, and the transformation of the 



