ORGAN AND BODY SYSTEMS 501 



gall bladder is more sensitive than the gastro-intestinal tract. This has 

 not been reported by any other workers and has not been within the 

 reviewer's experience. The illustrations published by Brahms and Dorn- 

 backer show in some cases, thickened, infiltrated gall-bladder walls 

 suggesting chronic inflammatory changes, rather than changes typical 

 of damage due to irradiation. This possibility should be eUminated 

 before it is accepted that the gall bladder is very sensitive to 

 radiation. 



LUNGS AND HEART 



Lungs. — It is the opinion of the reviewer that the structures within 

 the lungs are relatively resistant to irradiation. The stroma which is 

 composed mainly of connective tissue and blood and lymph capillaries 

 is not very sensitive to ordinary "therapeutic" dosage, and there is very 

 little evidence to support the proposition that the bronchial-alveolar 

 epithelium is very sensitive, i.e., more so than the skin. The pleura must 

 likewise be quite resistant, in fact almost as resistant as the skin. Dosage 

 above the human erythema dose either as a single massive dose or as 

 fractional dosage, or where the lung is struck by converging ("cross 

 fire") beams of high dosage, may w-ell cause damage (70, 73, 94, 131, 205). 

 Here, too, the damage may be related to the most resistant cells of the 

 organ. The blood-vessel endothelium is apparently less severely dam- 

 aged than the bronchial epithelium, which may swell and even necrose 

 (Ludin et al., 205). In this state secondary infection is prone to happen 

 in experimental animals and presumably in human cases. The pleural 

 inflammation may be noted along with that of the skin and lung paren- 

 chyma. The mediastinal structures with the exception of the thymus 

 and lymph nodes react about the same as the pleura to equivalent dosage. 

 Caution should be used in interpreting mild changes found in the lungs 

 because of the common finding of some pneumonitis in ordinary animals 

 kept under laboratory conditions (403, 404). Capillary damage, edema, 

 evidence of injury to the bronchial and alveolar epithelium, localized 

 emphysema or atelectasis may be found without and with clinical evi- 

 dence of acute respiratory disease (62). Such changes may be rather 

 uniformly distributed throughout the animal colony. Changes such as 

 those described by the various workers (204, 205, 403, 404) following the 

 irradiation of the animal with very large doses are probably specific 

 changes brought about by irradiation. From the biological standpoint 

 the lungs are fairly resistant to irradiation. From the therapeutic 

 aspect, in the face of crossfire and extensive fractional dosage procedures, 

 the lung may suffer extensive damage and even be severely enough 

 injured to cause death. Human cases under treatment by radiation, 

 however, cannot be freed from the suspicion that the amount of neo- 

 plastic involvement of the lung substance and pleura was responsible to a 



