34 BIOPHYSICALLY ACTIVE X-RAYS 



The coagulating power of the blood (Lindhardt [1924]) is not affected 

 except in therapeutic cases irradiated for castration or hyperthyroidism, 

 where it is found to fluctuate in amount. 



The most sensitive cells in the testis, according to Feroux and Regaud 

 [1927], are the basal cells or spermatogonads. The adult sperms are 

 apparently insensitive, since they show no change after irradiation. 



S. L. Warren [1928], in a review of the physiological effects of roentgen 

 rays upon normal body tissues, lists the tissues in a descending scale of 

 sensitivity, beginning with a moderate sensitivity, in the following rough 

 order: thymus, stomach, colon, and bladder epithelium; salivary epi- 

 thelium; probably kidney epithelium; hair papillae; blood-vessel 

 endothelium; fibroblasts; and young connective-tissue cells including 

 collagenous fibrils. Next in order of decreasing sensitivity are: the 

 mucosa of the mouth, esophagus, rectum, and vagina; the lung paren- 

 chyma; pleura; skin epithelium; and the structures of the eye. Next 

 come the smooth, striated, and cardiac musculatures; cartilage; bone, 

 including osteoblasts; teeth; normoblasts; Sertoli's cells; and stroma 

 cells of testes and ovary. The most resistant cells may be listed in the 

 following order: adult thyroid, adult pituitary, brain and nerve cells, 

 nerve trunks and endings, tendons and joint capsules, adult sperm cells, 

 and red blood cells. 



Latent Period 



In a review of the literature on the latent period Regaud [1925] points 

 out that sensitive cells of the epidermis are the generating cells of the 

 basal layers, and that the changes in the skin occur as these cells are 

 elevated toward the cornified surface. The period of latency is a meas- 

 ure of the time which is necessary for the cells from the basal layer to 

 reach the cornified stage in their progress to the surface. The same is 

 true of the testes, where the sensitive cells are the spermatogonads. 

 Until time has passed to allow successive generations of cells to reach 

 maturity, the injury is not apparent. This is the latent period for the 

 spermatozoa. The thymus cells are very sensitive to radiation and 

 have a very short latent period. This latent period conforms to the 

 interval of time extending from the death of these very sensitive cells, 

 in this case the lymphocytes, to the disintegration and absorption of the 

 cell bodies. 



An important biological effect of x-rays and 7-rays is the increase 

 produced by them in the rate of mutation of genes. All types of muta- 

 tion occur, but none have been observed which may specifically be 

 attributed to x-ray absorption. The interpretation seems to center 

 around the concept that "one direct hit" (Crowther [1924]) suffices 



