ORGAN AND BODY SYSTEMS 507 



or mechanical disturbances from the appUcation of the radium, confused 

 the issue so much that very Uttle definite data concerning the effects upon 

 the normal ear systems are available. Girden and Culler (117) gave 

 various amounts of radiation at 50 to 85 kv. with various filters to dogs 

 over the ear; the doses varied from 400 r in 18 weeks up to 11,162 r in 

 25 weeks. They obtained severe damage to the skin and an anemia. 

 With very careful testing they seemed to show an initial rise in auditory 

 acuity following small doses, but this lasted 2 to 3 weeks only. Deafness 

 was not produced. The experiments may be criticized by the suggestion 

 that the dosage was spread over too long a period of time and the con- 

 clusion may be drawn that huge amounts are necessary to bring about 

 changes, partly because of the position of the ear within the bony struc- 

 ture and partly because of the difficulty in delivering a high dosage with 

 this low voltage to the auditory mechanism. It is very likely that if 

 this problem is investigated it will be possible to show damage to all 

 parts of the structure of the inner ear. The muscle attached to the 

 drum, the blood vessels, and the nerves are probably as resistant to 

 radiation effects here as elsewhere unless the proper depth dose is 

 administered. 



NERVE TISSUE 



Brain. — Lyman, Kupalov, and Scholz (206), in the best review of the 

 German and Russian literature (cf. 215, 288, 401) find general agreement 

 that roentgen irradiation in therapeutic doses causes no damage to the 

 adult central nervous system or to its function. Intensive irradiation 

 may cause changes in blood vessels and perhaps temporarily reduce the 

 secretion of the spinal fluid (68). While the radiation in 18 to 20 human 

 erythema doses may alter the function of the central nervous system, 

 this does not seem to be due to primary action upon the cells of the 

 cortex (206). The excitability of the cortical cells may be lowered, 

 as determined by conditioned reflexes, but this seems to be secondary to 

 changes in the blood supply. The irradiation, even when directed at a 

 single area, causes a diffuse physiological and pathological effect, involv- 

 ing the subcortex as well as the cortex and probably also the vegetative 

 nervous system. Histological studies show diffusely scattered degenera- 

 tive change in the precapillaries and capillaries of the brain within 6 

 weeks. One dog, allowed to live 6 months, exhibited signs of diffuse 

 damage to the functions of the cortex and subcortex, i.e., ataxia, tremb- 

 ling, and weakness. Histological studies showed advanced degenerative 

 changes with hyalinization and obliteration of the arterioles and several 

 extensive areas of necrosis in the brain. Direct injury to the nerve 

 parenchyma by irradiation is not probable in view of the focal destruc- 

 tion of fibers in the chiasm and nature of the diffuse degenerative changes 

 which vary in different places. Furthermore, the lesions were no less 



