502 BIOLOGICAL EFFECTS OF RADIATION 



great extent for the fibrosis and other changes reported (70, 73, 94, 101, 

 131, 238, 356). 



Blood Pressure. — There is Httle or no evidence that roentgen rays 

 induce changes in blood pressure. Stephens and Flory (344) irradiated 

 unanesthetized rabbits with large doses and failed to find any alteration 

 either in blood pressure, in the respiratory rate, or in the size of the 

 spleen or other abdominal viscera which they viewed through an abdomi- 

 nal window. This is also the opinion of Desjardins and Marquid (70) 

 who have made an extensive study of this subject. When human 

 patients with tumors are irradiated, a fall in blood pressure, lasting from 

 1-35 days may occur (263). But in all probability this reaction is not 

 due directly to the radiations but rather to the disintegration products 

 of the cells destroyed by them. The results of Swann (345), which 

 appeared to indicate a fall in pressure following exposure, may have been 

 due to currents set up in the apparatus by the roentgen equipment. 



Heart Muscle. — Animal experiments indicate that the specific radio- 

 sensitiveness of the heart is relatively low, probably near the tolerance of 

 smooth muscle and blood-vessel muscle, and much lower than that of 

 many other structures. Doses of roentgen rays even beyond the amounts 

 usually employed in the treatment of human patients probably have no 

 effect on the heart. Experiments with rabbits indicate that single doses 

 of about 600 r produce no definite change in the size of the heart, in the 

 histology of the myocardium, or in the nervous mechanism (111, 114, 127, 

 332, 349, 378). The same is true when the radiation is given by the 

 simple fractional or protracted fractional method, with a total dose of 

 7000 r (403). Even 5 months after treatment no sign of injury is found. 

 Kawashima (172) was unable to find any changes in the contractile rate 

 or power of isolated frog heart muscle after intense roentgen radiation 

 or immersion in radioactive Ringer's solution. Desjardins (73), in 

 summarizing the clinical reports, finds a few instances of apparent injury 

 from radiation but concludes that such effects must be ascribed to indirect 

 factors, such as injury to the pleura and lungs or to the circulation of 

 toxic products induced by the rays in other organs. 



The heart is not entirely insensitive to radiations and may be injured 

 by doses of sufficient strength. The damage appears in the blood 

 vessels, in the muscle cells, and in the conductive system. The early 

 effects of large doses and the late effects of small doses on the blood 

 vessels of the heart consist of an initial engorgement and a later necrosis 

 followed by a rupture of the wall and consequent hemorrhage into the 

 surrounding tissue (26). A thickening of the walls and even an obHtera- 

 tion of the lumen are also reported (136). Fedder and Kellner (99) find 

 irreparable damage to the nuclei of the cells. 



Changes in the muscle are described by Warthin and Pohle (379) 

 who employed multiple exposures. The fibers present a rather "wooly" 



