Diseases of Arteries. 347 



attached is intensely and unnaturally red, and a rough granular 

 surface has given place to the healthy, smooth glistening appear- 

 ance. In old standing cases the clots can only be separated from 

 such surfaces by dissection with the knife. Other portions of the 

 surface than those to which the clot adheres are usually smooth 

 and polished, though rough granular and injected patches are 

 sometimes met with independently of clots. 



The mu.scles formerly supplied with blood by the obstructed 

 arteries are pale, discolored, unnaturally firm, and if some time 

 has elapsed since the plugging their fibrillated structure is made 

 out with difficulty. 



Causes. The causes of arteritis are often obscure. Goubaux 

 conceived that it was frequently determined by extreme mu.scular 

 tension. In support of this view he adduced the facts that it has 

 been mainly observed in the horse, in which such stretching of 

 the muscles is greatest, and that its most common .seats have been 

 where the muscles and vessels are most liable to stretching. 

 Thus it is frequent in the posterior aorta towards its termination 

 or in other words where the adjacent muscles (psose) are very 

 liable to laceration from slipping backward or from efforts to dis- 

 engage the limbs when fixed in soft ground ; the femoral and 

 auxiliary arteries are likewise frequent seats of inflammation and 

 are likely to be overstretched when the limbs slip outwards. 



Embolism or Plugging of the arteries must be accepted as 

 another cause. This is referred to under endoca7-ditis, as an oc- 

 casional consequence of the detachment of clots and fibrinous 

 substances from the internal membrane of the heart. The de- 

 tached mass in this case passes from the heart into the aorta and 

 thence through its divisions until it reaches a vessel too small 

 to receive it, when it is at once arrested and determines inflam- 

 matorv action in the plugged vessel. When arrested in some 

 soft organ such as the lungs, liver or brain the resulting inflam- 

 mation often gives ri.se to extensive suppuration and abscess. In 

 other situations its effects may be confined to inflammation, the 

 shutting off, of blood from particular parts, the impairment or 

 loss of their function and nutrition, and finally atrophy and de- 

 generation. 



But the heart is not always the primary .source of such clots. 

 Virchow and others have demon.strated by post mortem examina- 



