390 EXPERIMENT. [BOOK II. 



that if the blood that is left behind in the fine 

 capillary vessels be ever so good and proper for its 

 purpose at first, yet the very circumstance of its re- 

 maining idle causes an inflammatory heat, that at- 

 tracts toward itself all such congenial particles of 

 the blood which may have been sent through the 

 arteries to the part for the propagation of new horn, 

 or the supply of marrow — of the nature whereof 

 the matter of grease partakes. Indeed, we have 

 very little doubt that the marrow is concerned in 

 the production of grease ; for, after successively 

 examining twenty legs which were affected with 

 grease at the time life was extinguished, the marrow 

 was found invariably confined to the lower part 

 only, as if it were fallen down there for want of 

 vigour, w r hilst the upper part of the bone was 

 hollow, in every instance. Healthy leg bones 

 are always full to the top of each, and we have 

 reason for thinking that the contrary is the case 

 with all debilitated horses. Again, the glutinous 

 substance that pervades the surface of the coffin 

 bone, and to which we attribute the formation of 

 new horny matter of the hoof, is always found 

 scanty in greasy-heeled subjects. See observations 

 on t/iefoot, in Book iii. 



One of those legs parted from the knee, having 

 the skin removed, but otherwise untouched, was 

 hung up in the yard whilst the sun was at 70 de- 

 grees (July 1825). In three or four days the 

 grease might be seen to give a colour to the lower 

 part of the fetlock joint, and every day the greasy 



