2^8 ^ Internal SECRETIONS ' 



want of agreement between the statements of the different 

 authors could be explained by the following factors :. 



(a) Differences in the technique of irradiation. 



(h) Differences in the species, age and size of the animal. 



(c) Differences in the time between irradiation and histo- 

 logical examination; if the latter is done too early the 

 changes which irradiation induces will not have been 

 completed. 



(d) Incomplete histological examination. 



The third factor is of an especial importance. It is 

 impossible to discuss properly the results af irradiation without 

 taking into consideration what may be called the histological 

 dynamics of the ovary. Two fundamental facts must be the 

 starting point in every discussion of this kind; first, that the 

 interstitial cells are less sensitive to X-rays than the follicles, 

 i.e., the ova and the cells of the membrana granulosa (see 

 below, p. 230), and secondly, that the interstitial tissue, if persist- 

 ing, has to be provided from time to time with new cells from 

 the folhcles undergoing atresia. Realising this one will be able 

 to understand that by decreasing the strength of irradiation 

 the following three separate results will be brought about, 

 without the sensitiveness of the ovary having been different. 



First case. Degeneration of both ova and follicles and inter- 

 stitial tissue, which will be replaced by common connective 

 tissue. 



Second case. Degeneration of all ova and follicles, while the 

 interstitial tissue is injured only slightly or not at all; but as the 

 interstitial tissue can persist only when provided with new 

 cells by follicles, degeneration of follicles will result after a 

 certain time in a reduction and disappearance of the interstitial 

 tissue. 



Third case. Injury of the follicles without full degeneration 

 of ova but increased atresia; by this a great number of inter- 

 stitial cells will be provided by the obliterating follicles, and an 

 increase in the interstitial tissue will occur. 



As Lacassagne stated, the sensitiveness of the follicle seems 

 to be different according to the degree of its development; in 

 view of this factor the reaction of the ovary to X-rays will 

 become still more manifold. Further, it seems clear that there 

 will be also transitions between the cases mentioned above; 



