ORGAN AND BODY SYSTEMS 497 



The anatomical and histological picture resembles that of the third day. 

 During this whole period there is no evidence of damage to the skin. In 

 spite of the almost complete destruction of the mucosa of the small 

 intestine which is almost denuded of its protective mechanism, indeed 

 the muscularis mucosa is bare in many places, the body usually is not 

 invaded by an overwhelming number of bacteria (374). 



All of the common experimental animals respond in the same manner 

 to doses of 2000 to 2500 r over the abdomen. Divided doses given 

 within a 5- to 6-day period cause practically the same effect as a single 

 massive dose equal to the sum of the small doses. But when exposures 

 are given at intervals of 5 days there is no evidence of a summation 

 effect (375). The rat and guinea pig are slightly more sensitive than the 

 dog, cat, and rabbit. By contrast, birds, frogs, and reptiles, are very 

 resistant and may tolerate doses two or three times as great as the lethal 

 dose for dogs (373, 375). 



Exposure to large doses of roentgen rays will cause notable increase in 

 the speed of autolysis (372) of the crypt or secretory epithelium of the 

 dog's small intestine. These changes can be demonstrated readily in 

 material obtained from dogs sacrificed 2, 24, 48, 72, or 96 hr. after the 

 initial radiation. In the irradiated dogs the secretory crypt epithelium 

 of the small intestine autolyzes first and the epithelium of the villi last, 

 while the reverse is true in the normal control small intestine. The colon 

 shows little change and the stomach no demonstrable changes in autoly- 

 sis under like conditions. The kidney likewise is unaffected. The 

 spleen, lymph glands, liver, and the pancreas show a moderate increase 

 in the speed of autolysis only in tissues taken from irradiated animals 

 within 48 hr. of the initial exposure. What the significance of this dis- 

 turbance of cell ferments in the intestinal mucosa may be, one cannot 

 pretend to say. At least these observations strengthen one's confidence 

 in the profound functional disturbance of this important intestinal 

 epithelium — a disturbance which it is believed is responsible for the 

 clinical abnormalities and fatal intoxication occurring in these animals. 



Martin and Rogers (208) studied the chronic lesions in the small 

 intestines of dogs receiving various amounts of dosage over the abdomen 

 (with approximately 100 kv.). The animals developed ulcerated areas 

 when small doses were given, which were followed by cachexia and death 

 in 2 or 3 weeks. Damage to a single isolated loop resulted in a more 

 slowly progressive cachexia with exitus in 2 months with intestinal 

 ulceration and occasionally obstruction. The fat absorption was 

 inhibited and the mucous secretion was increased. 



Further work with chronic or acute lesions in the small intestines 

 may lead to an explanation of the intoxication which occurs from the 

 acute injury, as pointed out by some workers (371), for this is apparently 

 closely related to the intoxication found in intestinal obstruction and 

 the clinical disturbance noted after intensive irradiation of patients. 



