176 XEUTRON EFFECTS ON ANIMALS 



45th Day. The tubules (Fig. 9) were free of cell debris and were more 

 shrunken. A few tubules were regenerating. 



60th Day. The changes were essentially the same as at 32 or 45 days, 

 except for one or two foci of infiltration of lymphocytes into the interstitial 

 tissue. A few spermatids were being formed in a few regenerating tubules. 



75th Day. The number of regenerating tubules (Fig. 10) was slightly 

 greater than at 60 days and a few contained scattered spermatocytes, 

 spermatids and spermatozoa. 



90th Day. The changes were not uniform, ranging from a well advanced 

 regeneration to extreme atrophy. 



103rd Day. Most of the tubules were normal in size with spermato- 

 genesis well advanced. In a few tubules sperm formation was complete. 

 Occasional tubules remained extremely atrophied and consisted only of a 

 syncytium of Sertoli cells. Edema was present among the atrophied 

 tubules. The interstitial cells appeared normal (Fig. 11). 



120th Day. Regeneration was almost complete, with spermatogenesis 

 and sperm formation (Fig. 12). The number of sperm was less than nor- 

 mal. The interstitial tissue had become less prominent and appeared 

 normal in amount. A few tubules remained atrophied. 



150th Day. The tissue appeared normal except for a few tubules which 

 were atrophied and consisted only of Sertoli cells. Otherwise the tubules 

 showed a complete cycle of spermatogenesis, somewhat less active than 

 normal. 



200th Day. Same as 150th day. 



113 n. During the first 24 hours no structural changes were observed. 



2nd Day. Mitotic activity had ceased in most tubules. There was a 

 slight irregularity in staining in a few of the secondary spermatocytes 

 which showed pycnotic nuclei. 



4th Day. Degeneration of the central tubules (Fig. 13) was marked. 

 Although there was no spermatogenesis, the primary spermatocytes and 

 numerous sperm were morphologically normal. Many tubules were atro- 

 phied and their lumina filled with detached cells undergoing degeneration. 

 Edema fluid was present in the interstitial spaces. Comparison of Fig. 13 

 with Fig. 6 shows that the injury caused by 113 n was much greater after 

 4 days than that caused by 56.4 n. 



8th Day. Degeneration had progressed further but otherwise the con- 

 dition was the same as at the 4th day. 



11th Day. There was marked variation in the amount and degree of 

 atrophy (Fig. 14). some tubules being normal in size, others shrunken with 

 irregular outlines. The most degenerated tubules consisted mainly of 

 minutely granular, dull red-staining material which was darker in color 

 than normal tubules and was without any visible cell outlines. In other 



