This article is only available in the PDF format. Download the PDF to view the article, as well as its associated figures and tables. Investigations by Hauss, Junge-Hülsing, and Gerlach convinced them that the nonspecific mesenchymal reaction is pathogenic in arteriosclerosis, myocardial sclerosis, myocardial necrosis, myocardial infarction, rheumatic illnesses, and diabetic angiopathy. They found that a great variety of noxious stimuli can produce a similar disturbance in mesenchyme which responds by proliferation. Incorporation of sodium sulfate S35 into the acid mucopolysaccharides has served them as an index of the metabolism of mesenchyme. In the broad series of diseases considered, the metabolism (synthesis and breakdown) is increased. Ordinarily, synthesis exceeds breakdown and thus increases the mass of mucopolysaccharide. This increased mass can be demonstrated by electronmicroscopy; it broadens the transitdistance between capillaries and cells and disturbs their metabolic interchanges. The reverse may also occur with loss of mesenchymal mass. In either event, the irregularity of the process results in uneveness in the anatomical relationship between circulating fluids and the cells dependent upon them for life.