HEMATOLOGIC EFFECTS OF RADIATION 



1047 



tends to implicate the platelet in preservation of the integrity of the 

 capillary wall. On the other hand, increased capillary fragility and 

 petechial hemorrhage are observed in a number of toxic states, including 

 severe systemic infection, even though platelet values of the peripheral 

 blood are normal. The importance of the widespread microscopic hemor- 

 rhage that occurs presumably secondary to direct or indirect injury to the 

 capillary wall has recently been emphasized by Furth et al. (1951) . Even 

 in the absence of gross hemorrhage a more severe anemia occurs after 

 whole-body exposure to dosages above the LD 5 o than can be accounted for 



en o 

 IF 



2 4 6 8 10 12 14 



TIME AFTER X RAY. days 

 'CLOTTING TIME o o PLATELETS 



16 



Fig. 16-11. Effect of a 450-r single dose of total-body roentgen irradiation on the 

 platelet values and clotting time (Lee- White) of 25 dogs. {Allen et al., 1948.) 



by cessation of erythropoiesis alone. Furth explains this discrepancy on 

 the basis of increased microscopic hemorrhage resulting from "leaking" 

 through the capillary walls. No histologic abnormalities have been 

 demonstrated that account for this loss of vascular integrity. 



HEMATOLOGIC EFFECTS OF CHRONIC TOTAL-BODY EXPOSURE 



TO EXTERNAL RADIATIONS 



The penetrating radiations to which laboratory animals have been 

 exposed chronically (repeated or continuous exposures) include X rays, 

 7 rays (radium and pile gammas), fast neutrons (cyclotron and pile- 

 produced), and slow neutrons. Survival, carcinogenesis, and other 

 biological effects have been studied in several species of mammals after 

 exposure to these radiations. Adequate hematologic studies have been 



