ORGAN AND BODY SYSTEMS 519 



common and indolent. Blood vessels tend to thrombose in such areas 

 (12, 393). 



Wierig (386) reports a late injury with atrophy of the breast structure 

 of a young girl (17 years of age) who had received intensive short-wave 

 irradiations over the chest for mediastinal tumor. There were skin 

 changes and atrophy of the thorax muscles. 



The capsule of the thyroid in the dog is thickened only by dosages 

 which would produce skin ulcers (366). There is some tendency to 

 hyperplasia of the normal thyroid and parathyroid. Within several 

 months after irradiation there is an increase in the connective-tissue 

 stroma of the parathyroid with a slight decrease in the blood calcium. 

 The dosage used (4 to 12 doses of 375 r) at 7 to 14-day intervals indicated 

 that clinical dosage did not affect the parathyroid and has relatively little 

 effect on normal thyroid tissue. 



The hyperplasia of the thyroid gland which occurs in opossums on a 

 high-protein (meat) diet was definitely decreased, but not entirely pre- 

 vented, by the irradiation with 385 r, at weekly intervals for 4 to 12 doses 

 (367). 



Lenz (196) exposed the thymus glands of young rabbits to very small 

 doses of 200-kv. radiation, i.e., one thirty-fifth H.E.D. and less without 

 demonstrating any stimulating effect from these small doses but on the 

 contrary found that the normal resolution occurs more rapidly after the 

 exposure to this intensity (cf. 398). 



These changes are hardly within the scope of this review because of the 

 wide ramifications such a discussion would entail. Too often the results 

 are obscured by the fact that the irradiation is directed into a tumor 

 mass so that the results (115, 126, 145, 333, 395) are of interest from the 

 clinical standpoint but not indicative of normal tissue changes. Much 

 of the work in animals is likewise difficult to correlate because of the 

 absence of suitable standards for normal findings under controlled labora- 

 tory conditions in these animals. The type of animal used varies a great 

 deal. The amount of dosage and the tissues irradiated must influence 

 the result tremendously (48, 56, 63, 82, 83, 136, 148, 155, 164, 203, 276, 

 279, 300, 353, 369). This is very seldom considered. All too frequently 

 the chemical changes in the blood are not correlated with a careful study 

 of the kind or the extent of injury produced (functional and anatomical) 

 in the tissues irradiated. Much of the animal experimental work is done 

 with too low dosage (H.E.D. or less) usually in the expectation of 

 postulating similar observations (usually negative) upon human cases 

 (63, 271, 279). When obtained, the results are not directly comparable. 

 Adler and associates (2, 3, 4, 5), for instance, exposed rabbits to 1000 r 

 over the backs and obtained a decrease in the blood-sodium level of 

 from 6 to 15 per cent. In ill patients treated with roentgen or radium 

 radiation in their clinic no such changes were found. 



