Diseases of Arteries. 485 



though it sometimes shows branching redness and thickening 

 from exuded lymph. The internal coat where the clot was 

 attached is intensely and unnaturally red, and a rough granular 

 surface has taken the place of the healthy, smooth glistening 

 appearance. 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 muscles 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 muscular 

 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 

 axillary 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 endocarditis, as an oc- 

 casional consequence of the detachment of clots and fibrinous 

 substances from the internal membrane of the heart. The 

 detached 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 

 inflammatory action in the plugged vessel. When arrested in 

 some soft organ, such as the lungs, liver or brain, the resulting 

 inflammation often gives rise 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 degeneration. 



