OVARIAN MODIFICATIONS IN STERILITY 331 



unshed ova were discernible. These observations bear out Evans' (1924) 

 interpretation that corpus luteum substance develops precociously under 

 such circumstances and imprisons the ovum. 



In a second experiment the oestrous cycles of nineteen rats injected 

 with anterior pituitary substance was followed by means of daily micro- 

 scopical inspections of vaginal smears. It was found that the cycles became 

 irregular with a tendency for the dioestrual period to be much prolonged. 

 Inhibition of fertility occurred as in the previous experiment with injected 

 anterior lobe substance. 



EXPERIMENTS WITH TESTICULAR NTJCLEOPROTEINS 



In the first experiment seventeen female rats were given intraperitoneal 

 injections of testicular nucleoproteins from one to three times over a period 

 of some four weeks. Four of the animals eventually bore young and four 

 would not mate. Although the remaining nine were observed to copulate 

 and living spermatozoa were recovered from their vaginas the individuals 

 all remained sterile until discontinuance of the experiment some months 

 later. In several of the latter, prolonged dioestrum followed mating but 

 whether this was a pseudopregnancy induced by mechanical stimulation, 

 such as is known to occur sometimes, or the result of some form of endoc- 

 rinal imbalance is uncertain. 



A second experiment, with lighter dosages of testicular nucleoprotein 

 extract was conducted with 50 experimental and 17 control rats. The 

 oestrous cycle was followed by means of microscopic inspection of daily 

 smears. When a rat showed evidence of resuming its regular cycle the dose 

 was increased. The results showed that the cycle was generally rendered 

 irregular, with prolonged dioestrual periods. In most of the animals fer- 

 tility returned, at least in part, in about six weeks after the cessation of 

 injections. 



Sections of the ovaries of rats rendered temporarily sterile by injection 

 of nucleoprotein usually showed an increase in both the number of corpora 

 lutea and of follicles containing unshed ova. In some follicles ova were in 

 process of disintegration; in others, a fragmentation that suggested pre- 

 cocious cleavage had occurred. There was no evidence of premature lutein- 

 ization such as seemed to occur in sperm-injected rats. 



The pituitary anterior lobes of rats rendered sterile by nucleoprotein 

 injections showed a marked increase in the number of basophile cells in 

 comparison with the oxyphile and chromophobe cells. The condition 

 strikingly suggested that seen in castrate animals or in those to which 

 cancer has been transplanted. While in females there was slight if any 



