ne problem of selecting the right dose has been approached. — It is] well known that the histological structure of glands that cause hyperthyroidism is htuite variable. That variability appears to have considerable bearing on the effectiveness of the size of the dose of 131, required. Although we have not resorted to biopsy before treat- ment is given, much has been gained from reviewing the histologic features of all glar thoroughly studied and characterized before surgery and then by usihg those clinical features (hardness, softness, lobulation, nodularity, bruit, etc.) [to estimate the Structural character of the particular gland that is to be irradiated. This has appeared to be as important as the weight or size of the gland because much of the volume may not be composed of thyroid cells. With the limited rangq of the beta ray within the thyroid gland,ionization may take place in structures distributed among thyroid cells. roid cell. Thus, the ionizing effect may take place at sites qther than the thy- The gland may be extensively infiltrated with lymphocyfes, in which case, it will be more firm and rubbery on examination. In contrast a comsiderable part of its volume may be blood and as a result it will be very soft, compyessible and have a bruit. The gland may have become lobulated and thus involuted wit a considerable part of its volume occupied by colloid with only spotty areas of hyperplasia. from the radioautographs that the 13 ly is then taken up in a very We knc ottled pattern. Such a gland is lobulated and rather fim, but not as firm as when|infiltrated with lymphocytes. This gland often feels rather pebbly. The very hypefplastic gland witt few if any lymphocytes or colloid is composed of relatively more cRlls. Servations, we believe these intrinsic characteristics of the glanf play a major part in the effectiveness of the radiation. pied by lymphocytes, From our ob- of Grave's disea: The greafer the space occu colloid, or connective tissue the more ionizBtion is spent in these structures rather than in the cells that produce hormone. Spch characteristic: can only be inferred from a knowledge of the pathology as it relatks to the features of the physical examination. However, any physician or surgeon whp devotes a great