510 BIOLOGICAL EFFECTS OF RADIATION 



apparently killed the bone immediately around the irradiated area with 

 slow attempt at repair at the periphery. The periosteum, cortex, and 

 medullary contents were killed by the radium radiation. The dead bone 

 remained attached to the living bone and survived for 250 days. Frac- 

 tures occurred in some of his animals with overriding. If the bone is 

 not used for weight bearing, the necrotic bone will be sequestrated and 

 very slowly absorbed. 



Moderate doses of roentgen radiation caused a decrease in the quan- 

 tity of the callus of recently fractured bone in rabbits (109, 110) and 

 seemed to increase the speed of healing. Large doses caused no callus to 

 appear for 2 weeks and then there was an increase in the amount of 

 callus over the normal, but the total time for healing was greatly 

 increased. Others (247) found no change in the healing of fractured bone. 



Ewing (95) has described a form of chronic osteitis following irradia- 

 tion, a proliferative process which is probably secondary to harm done 

 rather than a primary stimulative reaction. Bone close to the skin 

 when irradiated heavily may develop a productive osteitis with hard 

 brittle bone. The periosteum being thickened and hyaline, flakes of 

 necrotic bone appear, and the shaft is greatly increased in thickness. 

 The bone marrow is deprived of its cells and is reduced to a mass of 

 mucinous fat and connective tissue. It may be necessary to lay down 

 entirely new bone, because to all intents and purposes the severely 

 irradiated bone is dead. This is especially true of intensive irradiation 

 of the jaw and ribs (20, 105). Similar sensitivity of bone to radiation has 

 been noted by Martland (212) as the result of the deposit of radioactive 

 substances in the bones of painters of luminous dials, in whom wide- 

 spread necrosis of the jaw occurred. Here also, as is the case after 

 roentgen irradiation, secondary bacterial invasion of bone injured by 

 radiation is a factor. The injury to bone in dial painters is much more 

 severe than has yet been described after roentgen irradiation, because the 

 action of the deposited radium and mesothorium compounds is con- 

 tinuous over a period of years. Furthermore, alpha radiation as well 

 as beta and gamma radiation has its source in intimate contact with the 

 cells and irradiates them intensely. In rats, 60 per cent of the material 

 injected was reclaimed from the mandibles (350). Such continuovis 

 action leads not only to necrosis of the shaft and increased calcification in 

 the ends of the bones (350) but also to diffuse radiation osteitis and to 

 injury to the hematopoietic system (212, 350, 360). As still another 

 possibihty in the chain of evils caused by the deposition of radioactive 

 materials in bone, Martland's (212) most recent contribution calls 

 attention to the occurrence of osteogenic sarcoma of bone in 2 radium 

 dial painters. 



Teeth. — Leist (195) exposed the jaws of young rats to large doses of 

 unfiltered radiation and found signs of definite injury to the odontoblasts 



