INTRODUCTION
Our conception of a satisfactory anatomical classification of thyroid changes is a scheme, composed of the major types of changes observed, arranged in the order of their manifestation and in which all separate or individual observations may find proper grouping. It is universally admitted that such a classification does not exist. It is, however, in connection with that group of anatomical changes embraced under the general term ``goiter'' that the greatest confusion exists.Studies based on large series of thyroids from the lower animals are still too few, though fortunately they are increasing because observers are realizing that human material is too complicated, and that the cataloguing of the almost infinite variety of possible histological variations has not simplified existing classifications or established the sequential relations of these changes. The multiplicity of terms now in use for each type of thyroid change is merely the result of