While an increasing number of workers are to be found in the field of the study of plastic flow, a fact which must appear rather disconcerting to the new student of the subject must be the great dissimilarity in viewpoint taken by the two schools of researchers in interpreting their data. While it is not proposed to undertake a complete analysis of the diverging conceptions obtaining, a few facts will be submitted which may serve to stimulate an enlightening discussion of the subject.