The quest ion of the aetiology of silicosis is dicussed on the basis of the available results from statistical investigations in the pneumoconiosis fre quency in coal-mining, from lung dust analyses, and from animal experi ments. The data achieved from lung dust analyses in many countries and from anima I investigations with artificial, quartz-containing dusts as weH as original dusts out of coHieries or isolated from human lungs are in favour of the opinion that free silicic acid in breathable particle size is aprerequisit for the origination of silicosis in coal-miners. There are other...

It is suggested that the stenosing effects of atherosclerosis may be offset by regression of the lesion, senescent dilatation of the arterial wall and by enlargement of anastomotic channels. Regression is slow and such inertia is attributed to: absence of cholesterol catabolic enzymes; disproportion of the ratio of LDLlHDL; physical inaccessibility of crystalline cholesterol; and relative absence of reticuloendothelial phagocytes. Moderate dilatation of the human coronary arterial wall with advancing age seems to compen sate for the inward encroachment of atherosclerosis on the lumen, hence...