THE HORMONES IN HUMAN REPRODUCTION 



which acts differently under different circumstances; but 

 the hypothesis that there are two has been generally accepted 

 as a working basis for further chemical research and for 

 speculation about the part played by the pituitary gland in 

 the menstrual cycle and in pregnancy. 



In the human species, the urine acquires during pregnancy 

 a gonadotrophic potency which appears to depend upon a 

 mixture of properties resembling those of FSH and LH. The 

 same is true for limited periods in the pregnancy of chim- 

 panzees and Rhesus monkeys. Whether the substances pro- 

 ducing these effects ("Prolan A" and "Prolan B" respec- 

 tively) are chemically and biologically identical with FSH 

 and LH, has been debated, and this question, like many 

 others relating to the gonadotrophic hormones, awaits the 

 final purification and identification of the substances. The 

 prolan-complex is undoubtedly produced by the tissues of 

 the placenta. 



The blood serum of pregnant mares contains a gonado- 

 trophic substance, believed to be produced by the placenta, 

 which because of some chemical peculiarity does not get into 

 the urine. This substance, known as equine gonadotrophin or 

 PMS (for pregnant mare serum), acts upon test-animals as 

 if it were a mixture of an FSH-like hormone with a small 

 proportion of LH-like material. The serum of pregnant 

 mares has been much used as a source of gonadotrophic 

 hormones by experimenters and drug manufacturers. 



A good review of this subject, bringing it up to 1945, will 

 be found in Burrows, Biological Actions of the Sex Hor- 

 mones, 1945. 



Note 12 (page 153, line 9). The coiled arteries. New 

 questions about the theory of menstruation, and particularly 

 about the. role of the coiled arteries, that have arisen since 

 the first writing of this book, are fully discussed in Note 13. 

 At this point, however, it will be well to modify the assump- 



{ e64 } 



