Ageing of Elastic Tissue 89 



elastic tissue of the media and tlie relations of such elastic 

 tissue changes to atheromata. "The only feature that is clear 

 is that the less definite a lamina (elastic) protecting the media, 

 the more definite is the atherosclerosis". Ophuls observed 

 that "the most important change caused by ageing of the 

 arterial wall is a gradual diffuse distension due to the pro- 

 gressive deterioration of the elastic tissue". Wells argued 

 strongly for the importance of elastic tissue failure in 

 arteriosclerosis. The fact is that a large volume of data had 

 been accumulated describing a characteristic fraying and 

 fragmentation of elastic tissue in arteriosclerosis, frequent 

 reduplication of the elastica interna, and development of a 

 profound affinity by elastic tissue for calcium salts. Curiously 

 enough, Anitschkow, who fathered experimental cholesterol 

 atherosclerosis, pointed out that lesions of the arterial wall 

 coupled with intimal fibrosis predispose to atheromata in 

 the presence of hypercholesterolaemia. 



It is quite understandable that Anitschkow's production of 

 atheromata by the administration of cholesterol resulted in 

 an intensive effort over the last twenty years to link arterio- 

 sclerosis to faulty lipid metabolism. These studies have been 

 strongly reinforced by the lipoprotein studies of Gofman and 

 of Barr, by the dietary studies of Keys, and by many others 

 too numerous to enumerate. As these studies developed it 

 became increasingly difficult to relate elastic tissue changes 

 in the arterial wall to the aetiology of arteriosclerosis. 



Our laboratory has been led to the conclusion that arterio- 

 sclerosis may be considered to be not one, but two diseases. 

 One disease involves a defect in cholesterol metabolism or 

 circulation, while the second disease is manifested by a 

 breakdown in the structure of tlie elastic elements in the 

 media of arteries accompanied by a calcification of this 

 elastic material. This point of view was supported by our 

 observations on human material that the elastic tissue break- 

 down occurs prior to the formation of atheromata, that the 

 changes in elastic tissue are associated with age and may 

 occur without atheromata (the converse is not true), and that 



