HISTOLOGICAL CHANGES AFTER IRRADIATION 1123 



man this may be temporary, appearing in about three weeks with doses 

 of 400 to 500 r of 200-kv X rays, but becoming permanent with 700 r or 

 more (Shields Warren, 1942, 1943). There are marked species differ- 

 ences in this respect, the laboratory mammals requiring about 2000 r or 

 more of X rays to produce permanent epilation (Ellinger, 1941). 



After temporary epilation in animals the hair may grow back white in 

 regions where previously it was pigmented (Hance and Murphy, 1926). 

 It has also been reported that regenerating hairs in man may be darker. 

 After a dose of radiation producing permanent epilation, the hair follicles 

 show vacuolation, cessation of mitosis, and focal necrosis. This is some- 

 times associated with a slight polymorphonuclear and mononuclear infil- 

 tration, but there is generally no intense leukocytic infiltration. 



During the first month the smooth muscles of the hairs increase in size 

 with some vacuolar degeneration (Wolbach, 1909), followed by increasing 

 atrophy, ultimately often disappearing completely. 



Nails. Occasional damage to finger nails has been reported. 



Skin Glands. The sebaceous glands are also highly sensitive, reduction 

 of their secretion beginning 5 or 6 days after exposure (Ellinger, 1941). 

 Usually one month after a dose of radiation causing permanent epilation 

 few sebaceous glands will be visible, and those persisting frequently show 

 some peripheral keratinization as well as accentuation of the basement 

 membrane. It is also claimed that the sebaceous glands are destroyed in 

 three to four weeks with a dose of 1200 r (Borak, 1936). The sebaceous 

 glands tend to persist longer than the hair follicles but not quite so long 

 as the sweat glands. 



The sweat glands are said to be as sensitive as are the hair follicles 

 (Flaskamp, 1930), a dose that produces temporary epilation decreasing 

 temporarily or inhibiting completely the secretion of sweat. There are 

 other reports which indicate that 2500 r is required to destroy these 

 glands (Borak, 1936). In the first few days vacuolar degeneration of 

 the epithelium is prominent, sometimes leading to great distinctness of 

 so-called "myoepithelial cells." About a month after irradiation, the 

 basement membrane is doubled or quadrupled in thickness, the lumens of 

 the glands have practically disappeared, and the connective tissue 

 adjacent to the coils is increased in amount and hyalinized. Later the 

 sweat glands may disappear completely. 



Mammary Gland. The duct system of the mammary gland, which 

 constitutes the epithelium of the resting organ, seems to be markedly 

 radioresistant. It has been reported that 2800 to 3600 r is necessary to 

 prevent the development of secretory acini in the rabbit (Turner and 

 Gomez, 1936). A dose of 720 r applied during the middle of pregnancy 

 inhibits the subsequent ability of the epithelium to secrete milk. Lacta- 

 tion is completely suppressed after 2800 r, and this will persist through 

 succeeding pregnancies. 



