496 BIOLOGICAL EFFECTS OF RADIATION 



that 1200 mg. el hr. of radium (0.5 Pb filter) produced a sharp reaction 

 in the mucosa of the lower esophagus when the apphcator was practically 

 in contact with its walls. The effect lasted from the tenth to the twen- 

 tieth day after exposure. Injuries following radiotherapy of the esopha- 

 gus are not common (74, 289). 



Stomach. — The gastric mucosa is much more sensitive than the esopha- 

 gus and may be damaged by doses which leave the skin unharmed. 

 Large quantities of radiation which cause epilation and necrosis of the 

 skin result in the destruction of the stomach wall and perforation. Such 

 lesions have been extensively studied (19, 64, 166, 374-377, 394). The 

 pathological changes involve chiefly the secretory epithelium. Dawson 

 (64) observed that the chief cells are the most sensitive while the parietal 

 cells are resistant. The latter, even when showing no histological 

 injury, are unable to produce acid. The decrease in the acidity of the 

 gastric juice is one of the characteristic reactions to radiation (64, 283). 

 Radium from an external source produces practically the same changes; 

 when applied locally its effect is very intense. If the dosage has not 

 been too great, repair follows injury. There is a proliferation of the 

 connective-tissue stroma and blood vessels, a realignment of a latent 

 atrophic mucosa. The regenerated mucosa is thin but histologically 

 normal. (For a review of the functional changes following irradiation 

 cf. Desjardins, 74.) 



Small Intestine. — The small intestine is considerably more sensitive 

 than the stomach, the sensitivity being manifested mostly in the crypt 

 cells of the viUi. This commences sharply at the pyloric sphincter and 

 extends to the ileocecal valve, the upper portion being more sensitive 

 than the lower. The effect of the radiations is proportional to the 

 dosage. In the dog a dose equivalent to the amount necessary to produce 

 epilation will destroy the entire mucosa (134, 207, 208, 377). 



Lethal doses of roentgen rays given over the abdomen of a normal 

 dog are followed by a physiological reaction of remarkable uniformity 

 (371). In the first 24 hr. the crypt epithelium shows a definite degenera- 

 tive change which begins to appear as early as 2 hr. after exposure. The 

 bone marrow, spleen, lymph nodes, and ovaries are also affected. During 

 the next 24 hr., necrosis of this epithelium may be almost complete, 

 while the tip epithelium of the villi remains practically intact. There 

 is little edema and invasion of wandering cells. On the third day the 

 small intestine from pylorus to ileocecal valve is raw and inflamed. 

 The crypt and villous epithehum has in large part vanished, leaving a 

 collapsed framework of mucosa in which there is some edema and inva- 

 sion of wandering cells. The disintegration of the mucosa is apparently 

 responsible for the symptoms and pathological lesions which develop. 

 The fourth day marks the peak of intoxication, and death usually takes 

 place at this time, preceded by vomiting, bloody diarrhea, and coma. 



