706 VI. OCCURRENCE OF LIPIDS IN THE ANIMAL 



aorta of human subjects which parallel their advancing age, no correspond- 

 ing increase in blood cholesterol has been noted. Moreover, Faber and 

 Lund 979 found that the progressive increase in the cholesterol content of the 

 aorta, which occurs with advancing age, is not altered by obesity. These 

 results have led many investigators to question whether atherosclerosis is a 

 result of hypercholesterolemia or whether it results from abnormal metab- 

 olism occurring locally in the intima of the aorta. 



On the other hand, there does appear to be evidence that hypercholestero- 

 lemia favors the production of atheromatous lesions in the rabbit. After 

 large amounts of cholesterol are given, 980 a deposition of lipids, consisting 

 mainly of cholesterol, occurs in the wall of the aorta. Although Leary 980 

 states that the individual lesions found in the intima of the rabbit are 

 similar to those found in arteriosclerosis in man, Rosenthal 974 considers that 

 they differ, in that they are far more diffuse in the rabbit. Moreover, in 

 the latter species, they are not confined to the aortic and systemic vessels, 

 but also occur in the pulmonary system, as well as in the veins. 981 ' 982 How- 

 ever, Duff 983 showed that, even in the rabbit, the injury to the aorta may 

 precede the deposition of cholesterol. This would indicate that the condi- 

 tion of hypercholesterolemia and of atherosclerosis can be dissociated in the 

 rabbit. However, the subsequent rate of deposition may be augmented or 

 exaggerated in the presence of high levels of cholesterol in the serum. 

 These facts would seem to indicate that the lipid metabolism of the rabbit 

 differs from that of man and, in fact, from that of most other animals which 

 fail to develop atherosclerosis when cholesterol is fed. This leads one to 

 question whether or not the results on rabbits may be applicable to man. 

 A discussion of the relationship of the plasma cholesterol level to athero- 

 sclerosis is included in Chapter V. 



979 M. Faber and F. Lund, Arch. Pathol, 48, 351-361 (1949). 



980 T. Leary, Arch. Pathol, 17, 453-492 (1934). 



981 R. Schonheimer, Arch, pathol. Anal Physiol. (Virchow's), 249, 1-42 (1924). 



982 R. Schonheimer, Arch, pathol. Anal Physiol. (Virchow's), 251, 732-738 (1924). 

 9 " G. L. Duff, Arch. Pathol, 20, 81-123, 259-304 (1935). 



