26 THE EGGS OF MAMMALS 



Simultaneous injection of beef and rat hypophysis tissue 

 results in inhibition of ovogenesis (column 3). 



When, however, examination was made of the ovaries of 

 animals receiving injections of growth hormone extracts 

 various results were obtained. In six of the ten animals ob- 

 served (column 7) the expected result was obtained, namely 

 an inhibition of ovarian growth and a rise in the rate of 

 ovogenesis. Two animals (column 8) with normal, good 

 sized ovaries exhibited a normal rate of ovogenesis, and 

 two animals (column 9) with somewhat decreased ovarian 

 weight gave no indication of increased ovogenesis. Two 

 interpretations of these data are possible: (1) the growth 

 hormone preparations may in some instances have con- 

 tained sufficient maturity hormone to overcome the typical 

 growth hormone effect or (2) there may have occurred in 

 some of the injected animals a conversion of growth hormone 

 to maturity hormone (c/. Evans, Meyer and Simpson, 1932; 

 Evans et at., 1933). It should be pointed out that Reiss, 

 Selye and Balint (1931a, h) have obtained from the pituitary 

 extracts free of growth hormone which also inhibit the 

 action of maturity hormone. Swezy's extracts are not made 

 in a manner that would free her preparations of such ma- 

 terials. Obviously the use of highly purified extracts and 

 carefully timed injections should assist in resolving the 

 situation. 



Pregnancy urine extracts (column 4) seem to increase 

 ovogenesis to some extent. It is known that pregnancy 

 urine is only partially effective as a maturity hormone 

 (Engle, 1929; Evans and Simpson, 1929). 



Prolonged oestrin injection is known to reduce ovarian 

 growth (Doisy, Curtis and Collier, 1931; Leonard, Meyer 

 and Hisaw, 1931; Spencer, D'Amour and Gustavson, 1932; 

 Pincus and Werthessen, 1933), presumably by inhibiting 

 secretion of maturity hormone from the anterior pituitary 

 (Meyer, Leonard, Hisaw and Martin, 1932). One would 

 expect therefore that the data of columns 5 and 6 should 

 show an enhanced ovogenesis. It is interesting to note 



