ATHEROMA. 427 



the existing histological elements pass directly into a state of fatty 

 degeneration and are destroyed, so that a larger or smaller proportion 

 of the constituents of the walls of the vessel perishes; and, in the next 

 place, a second series of changes, in which we can distinguish a stage o/ 

 irritation preceding the fatty metamorphosis, comparable to the stage 

 of swelling, cloudiness, and enlargement which we see in other inflamed 

 parts. I have therefore felt no hesitation in siding with the old view 

 in this matter, and in admitting an inflammation of the inner arterial 

 coat to be the starting point of the so-called atheromatous degeneration; 

 and I have, moreover, endeavoured to show that this kind of inflamma- 

 tory affection of the arterial coat is, in point of fact, exactly the same 

 as what is universally termed endocarditis, when it occurs in the 

 parietes of the heart. There is no other difference between the two 

 processes than that the one more frequently runs an acute, the other a 

 chronic course." 



INJURIES TO THE ARTERIES. 



In the lower animals accidents implicating arteries so as 

 to endanger life, are comparatively rare. It is nevertheless 

 important that the history of such injuries should be given, 

 as*they occur under circumstances when least expected, and 

 call for judgment in their management. From the account 

 I have already given of the structure of the arteries, it is evi- 

 dent that they are elastic vessels with coats sufficiently firm 

 to prevent collapse, and protected by an external sheath. 

 Professor Syme has shown that the inner arterial coat lace- 

 rates more readily than the outer ones, and when a ligature 

 is properly applied, its efficacy in arresting haemorrhage 

 depends not a little on the rupture of the inner coat, 

 whereby the caliber of the vessel is diminished, and the 

 formation of a plug favoured. The forcible tearing of 

 arteries is attended with an unequal laceration of the different 

 coats, the curling inwards of the elastic lining, and, conse- 

 quently, very slight, if any, haemorrhage. When, in castrating 

 small animals, the testicles are withdrawn so as to lacerate 



