- 18 - in cases with -sng-standing pulmonary hypertension. In costal cartilage there was no increase in ash with age and the alpha activity declined with age. Turner et al. and Mayneord were cited as having reported that the radioactivity of bone ash does not increase with age, In short, Elkeles reported that in those elastic arteries which are the most common sites of atherosclerosis, there is increase of both ash and alpha activity with age, and advanced the concept that progressive deposition of calcium together with small amounts of alpha emitters lead t> subtle injury and reactive changes of connective tissue in arterial walls leading to atherosclerosis, However, as mentioned above, there are changes in some parts of some vessels which precede and provide a receptive environment for deposition of calcium and the alpha emitters that behave like calcium metabolically and go with calcium, e.g., from bone to vessel walls. Much larger doses of alpha radiation than the amounts measured by Elkeles are required to damage arteries tothe point of causing substantial increase in calcium deposition. Increasing blood pressure with age should be highly suspect as one condition which may contribute to subtle but progressive changes in aorta, coronary arteries, and perhaps even renal and other arterioles to some extent, which may provide the conditions favoring calcium deposition. Just as atherosclerosis occurs in pulmonary arteries under the conditions of pulmonary hypertension, atherosclerosis in aorta or coronary arteries and damage of renal arterioles are associated with general hypertension or increases in blood pressure with age. Page 11, lines 4-7 - "In addition atherosclerosis plaques normally occur in the main and abdominal aortas and the coronary arteries, but / . : . : This distribution suggests rarely in the pulmonary arteries‘ 2,44) | a respiratory origin for the mutagenic agent."