120 EFFECTS OF AIR ON THE BLOOD. [BOOK I» 



taminated by any noxious stench (as the ammoniacal 

 smell of the stable, or the stench and smoke of 

 cities) ; no poisonous vapours (as burning brimstone, 

 the gaseous fluid, smelting of minerals *), nor infec- 

 tious effluvia (as of cesspools or stagnant waters, 

 producing fevers, glanders, &c.) can give to the 

 animal's blood that healthy vigour which was de- 

 signed for his well-being ; but, on the contrary, 

 every departure from purity in the air he breathes 

 must be an approach towards disease f. Yet, how 

 constantly is this simplest law of nature trans- 

 gressed 1 And what, in such a state of things, can 

 be expected, but that the blood will assimilate in 



* Scarcely any truth is easier proved than this : horses that are 

 constantly kept in close stables, in large numbers together, very soon 

 become unserviceable, by the constitution throwing off some evil or 

 other upon the surface ; as one proof whereof, those which are occa- 

 sionally placed in the under-ground stables, at the Swan with Two 

 Necks, Lad-lane, show evident signs of distress, which subside upon 

 being brought into the air. We hear from good authority, that at New 

 Orleans, in Southern America, where the atmosphere " exhibits a blue 

 misty appearance," nothing is more common than a disease which 

 affects the knee, hock, or pastern joint, with tumour, or near those 

 parts with a species of cancer, and the limb actually rots off. The 

 like kind of attacks were found formerly most common in Cornwall 

 and in Wales, and are attributed by all to the arsenical vapours of the 

 copper-mines being inhaled ; they are, however, much less frequent 

 at the present day, owing to the higher state of cultivation to which 

 the land has been brought, and to the change of situation horses now 

 enjoy. The free use of sweet oil is a good preventive of this poison 

 in human as well as in cattle medicine. 



t This is not the place for a finished dissertation on the communi- 

 cation of the glanders ; but we must observe, in illustration of the 

 text, that horses which have eaten glanderous matter without receiving 

 the infection, no sooner smell it than they become diseased. 



