404 LECTURE XVI. 



plates, which pervade the inner wall of the vessel, are 

 real plates of bone. Since they form out of the same 

 sclerotic substance from which in other cases the fatty 

 mass arises, and since a real tissue can only arise out of 

 a pre-existing one, it follows of course that, when the 

 process terminates in fatty metamorphosis, we cannot 

 assume this to consist in a simple dissemination of fatty 

 particles which has taken place in whatever interspaces 

 we like to fix upon. 



The essential difference which exists in a large vessel, 

 as for example, the aorta, between this process [athe- 

 roma] and simple fatty degeneration is therefore this, 

 that in the latter a very slight swelling arises on the 

 surface of the internal coat, a swelling, which at once 

 disappears if the superficial layers be removed by a 

 horizontal section, and beneath which there still remains 

 a portion of the coat unaltered. In the other case, on 

 the contrary, we have in the extreme stage a depot 

 which lies deep beneath the comparatively normal sur- 

 face, afterwards bursts, discharges its contents and forms 

 the atheromatous ulcer. This commences as a small hole 

 in the internal coat, through which the thick, viscous 

 contents of the atheromatous depot are squeezed out 

 on to the surface in the form of a plug ; gradually 

 more and more of these contents is evacuated and 

 carried away by the stream of blood, until at last there 

 remains a larger or smaller ulcer which may extend as 

 far as the middle coat, and indeed not unfrequently 

 involves it. We have therefore always to deal with 

 serious disease of the vessel leading to just as destruc- 

 tive results, as we see in the course of other violent 

 inflammatory processes. You need only apply these 

 observations to the history of endocarditis, and you will 

 have a correct notion of all that goes on there also. 



In the valves of the heart also we find simple fatty 



