426 CHARLES RUSSELL BARDEEN » 



direct and cy to-hereditary. The former represent direct cell 

 destruction, the latter alterations invisible in the exposed cells 

 but which make themselves manifest in abnormalities and degen- 

 eration in the daughter cells or cells of more remote descent. 

 Since the lesions do not appear for several days after irradiation 

 it would seem difficult to distinguish these two kinds of effects 

 from one another. In experiments on fertilized amphibian ova 

 in which the action of the rays can be more directly followed the 

 effects seem to be always of the cyto-hereditary type and hence 

 we should be inclined to believe it probable that such is also the 

 case in the testicles, although here doubtless the effects may some- 

 times become manifest at once in the daughter cells, at other 

 times not until several generations if cells have been produced 

 bj'^ division of the irradiated cells. 



Of the elements of the seminal epithelium the basal spermato- 

 gonia appear to be the most sensitive. The mitotic figures in 

 these cells and in those of the spermatocytes of the first order 

 arising from them become in large part abnormal and the cells 

 degenerate. In the experiments of Guyot we have seen that 

 irradiation with radium apparently stimulates the cells of the 

 Malpighian layer of the skin to hyperactive reproductive power 

 accompanied by involution of all the daughter cells instead of 

 only a portion of the daughter cells. It is not improbable that 

 a similar condition is produced in the generative epithelium of 

 the testicles. All of the daughter cells of the spermatogonia may 

 undergo involution which, however, is abnormal and abortive 

 in many of the daughter cells of the first generation. If the 

 irradiation has not been too severe a few spermatogonia may 

 remain for a time in a state of suspended activity and subse- 

 quently may begin to divide again and give rise to new genera- 

 tions of generative cells. At first, at least in the rabbit, man}" of 

 the cells of the new generations are abnormal in form. (Regaut.) 

 If the irradiation has been very severe the spermatogonia may all 

 disappear so that permanent sterility is produced. 



While Regaud attributes to the spermatocytes of the first 

 order a sensitiveness almost equal to that of the spermatogonia 

 it seems not improbable that many of the abnormal cells belonging 



