Atherosclerosis does not occure uniformly thoroughout the arterial system and each artery has its own charasteristics of atherosclerosis. I have conducted the following study in order to demonstrate a wide variation in the appearance of atherosclerosis at each artery. Aorta, coronary arteries and the arteries of the base of the brain were removed from a series of 154 unselected necropsy cases at Tokyo Medical Examiner's Office and atherosclerotic changes were classified into fatty streak, fibrous plaque and complicated lesion after staining with Sudan IV. These area was calculated by the scoring method and compared with each other.
1) In the aorta, fibrous plaque and complicated lesion increased almost rectilinearly after 20-39 years of age and abdominal aorta showed the most severe atherosclerosis.
2) The appearance rate of fibrous plaque reached its peak between 40-59 years of age in the coronary arteries, while that of complicated lesion between ages of 60-79 years. The sverity of atherosclerosis in the left anterior descending coronary artery was similar to that in the right coronary artery.
3) In the arteries of the base of the brain, the development of atherosclerosis was very slow, compared to other two arteries. The sverity of atherosclerosis of the arteries to be supplied with internal carotid arteries was not different from that of the vertebral and basilar arteries.
4) In the severity of atherosclerosis of these three arterial system, aorta showed the heaviest change, the coronary artery exhibited mileer ones and the change in the arteries of the base of the brain were the mildest. Slight positive correlation was found between the degree, of atherosclerosis in each artery and the specific susceptibility of each visceral artery to atherosclerosis was conspicuous.

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Since the days of antiquity, we have known that aortic circumference and length increase with advancing age. In this paper, a total of 103 specimens of aorta which were unselectively obtained from Tokyo Medical Examiner's Office necropsies were surveyed to study the correlation between aortic atherosclerosis and “senile ectasia”. Aorta was dissected longitudinally, fixed in formarin and then the circumference of aorta was determined at the ascending, arch, descending thracic, abdominal and the terminal portions of aorta. On the descending thracic aorta, aortic length was also measured and correlation between these changes and the age of the subject was studied. At the same time, aortic atherosclerotis index was calculated by method of Gore and Tejada, based on the quantitative value of aortic atherosclerosis which has been reported in the first part of this paper. Correlation between the aortic atherosclerotic index and “senile ectasia” of aorta was then studied. Following results were obtained.
1) All circumference of each parts of aorta increased straight along with advancing age and the rate of increase was larger at the proxymal aorta than distal.
2) The tendency of increase with advancing age was also observed on the length of thracic aorta above the age of 50.
3) The area of thracic aorta increased straight with its age, at a rate of 10cm² per 10 years.
4) Aortic atherosclerotic index was calculated by the method of Gore and Tejada. The relationship between age and this index indicated positive correlation in an exponential function.
5) Aortic atherosclerotic index increased with the aortic area in an exponential function.

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