568 



Prolongation of Pregnancy 



of estrous cycles in mice when lactogenic hormone was injected. Lahr and 

 Riddle" were able to demonstrate the same thing in rats. They inclined to the 

 view that the amenorrhea in mammals and human beings during pregnancy 

 and lactation is due to the presence of lactogenic hormone. Nathanson, Fevold 

 and Jennison"'^* believed that the experimental suppression of the estrous 

 cycle in mammals is due to the presence of luteinizing hormone in the com- 

 mercial preparations of lactogenic hormone. Evans, Simpson, Lyons and 



TABLE 2 

 Effect of Lactogenic Hormone on Prolongation of Pregnancy During Lactation 



Mouse No. 



74- 

 95- 



21 . 

 134- 



64. 



26. 

 135- 



121 . 



35-^ 

 lb 



31^ 



Dose 



iniected, 

 B.U. 



5 

 5 

 5 



5 

 5 

 5 



ID 

 ID 



ID* 

 ID* 

 20* 



Day of 

 injection 



3d 



3d 



4th 



4th 



6th 



7th 



4th 



6th 

 2d-8th 

 2d-8th 

 2d-8th 



Number 



of suckling 



young 



5 

 7 

 4 

 8 

 6 

 4 



3 

 6 



<; 



6 



5 



Prolongation of pregnancy 



Expected, 

 days 



Observed, 

 days 



7 

 1 1 



1 1 



no litter 



17 

 8 



no litter 



no litter 



10 



no litter 



no litter 



Difference, 

 days 



+ 0.7 

 + 2.3 



+ 5-9 



+9-5 

 + 2.9 



+3-7 



Average +4- 2 



* Divided in two daily doses. 



Turpeinen^'^ were able to produce deciduomata in hypophysectomized rats 

 with injections of pituitary lactogenic hormone. They were of the opinion 

 that lactogenic hormone increases the production of corpus luteum hor- 

 mone thus sensitizing the uterine mucosa for the deciduoma reaction. This 

 and the existence of functional corpora lutea during lactation, as well as 

 the release of hypophysial lactogenic hormone at delivery, made it worth 

 while to study the question whether lactogenic hormone injections during 

 lactation had the same effect on the delay of implantation as the corpus lu- 

 teum hormone. 



In these experiments lactogenic hormone of the anterior hypophysis was 

 used in the form of "Prolactin" manufactured by Eli Lilly %:. Company (In- 

 dianapolis, Ind.). This preparation is a yellowish powder, which is standard- 

 ized in pigeons (B.U.) according to the method described by Bates, Riddle 

 and Lahr.""" For these experiments it was dissolved in distilled water. The re- 

 sults appear in table 2. 



The results show conclusively that injections of lactogenic hormone into 



