Studies of Human Organ System Function 81 



unidentified, but statistically probable, number of cases of 

 peripheral arteriosclerosis. To this group, certain arbitrary 

 criteria are applied and a sample is selected for study. Either 



Fig. 4. Schematic method of obtaining a study sample. Indi- 

 viduals affected by disease are shown as if they could be gathered 

 within a shaded area ; clinical classifications are indicated as within 

 successive rectangles, in order to show that there is overlap and 

 disparity between disease and its clinical recognition. In the sample 

 selected for study, the relation between clinical classification and 

 disease identification may not be the same for young and old 

 subjects. 



by deliberate inclusion or by failure of exclusion, a number of 

 cases possessing arteriosclerosis will be present in our final 

 selected sample, Out of a fairly large number of subjects 



