HISTOLOGICAL CHANGES AFTER IRRADIATION 1131 



NERVOUS SYSTEM 



The nervous tissue of adult animals seems to be very resistant to injury 

 by irradiation (Shields Warren, 1942, 1943; Stafford L. Warren, 1936). 

 As might be expected, the nervous system of embryos and of newborn 

 animals does suffer severe damage, even after the period of multiplication 

 of cells is over (Snider, 1948b). The sheath and satellite cells seem to be 

 more sensitive than the neurons in the autonomic nervous system of 

 young chicks. 



EYE 



Shortly after the discovery of X rays it was found that irradiation pro- 

 duces a severe inflammation of the conjunctiva, and by 1908 it was 

 reported that cataracts very probably could be caused by irradiation 

 (Birch-Hirschfeld, 1908). Since then many studies have been made on 

 this subject and those before 1942 have been thoroughly reviewed (Poppe, 

 1942). It has been shown that 250 r produces permanent damage to this 

 organ in the rabbit (Poppe, 1942). All authors agree on the long latent 

 period required at approximately this dosage — as long as five to ten years 

 in man and at least five months in rabbits. Neutrons seem to be espe- 

 cially effective in producing cataracts (Evans, 1947). All mice exposed 

 to long-continued external j8 rays become blind owing to opacities of the 

 eye, presumably in the lens (Zirkle, personal communication). 



ENDOCRINE GLANDS 



Adrenal. The adrenal glands are among the more resistant organs, 

 and the reports of experiments involving them are unusually contra- 

 dictory (Desjardins, 1928; Shields Warren, 1942, 1943). This is in part 

 due to the extreme variations in the structure of the gland from species 

 to species and from animal to animal, and even in the same animal in 

 different physiological states. 



In rabbits no histological changes are found after 1500 r given at one 

 time, but degenerative changes in the cortex develop after higher doses. 

 It has been reported (Engelstad and Torgersen, 1937) that adrenals of 

 rabbits which received a single dose of 2200 to 2500 r of X rays locally 

 show marked degeneration in the cortex, particularly in the zona fascic- 

 ulata and the zona reticularis, but no irradiation effects in the medulla. 

 An initial transitory hyperemia between 1 and 3 days after treatment is 

 followed by a pronounced degeneration starting at 6 days and accom- 

 panied by hyperemia and often slight lymphocytic infiltration. The 

 changes are greatest and most constant three months after irradiation, 

 but are still found at six months. These authors point out a parallelism 

 between a visible skin reaction to X irradiation and noticeable effects on 



