88 G. I. M. SwYER 



remaining low. In the next cycle, 50 mg. ethisterone daily 

 was given from the 14th day of the cycle. There was no 

 tension (though the succeeding period was painful). Yet 

 again the Na/K ratio appears to have been on the whole 

 lower in the second half of the cycle. In the third cycle, no 

 treatment was given ; the usual premenstrual tension appeared 

 but this time the premenstrual Na/K ratios were the highest 

 in the cycle. 



It must be confessed that the writer does not know how to 

 interpret these findings, beyond concluding that they do not 

 provide evidence for theories currently held to account for 

 premenstrual tension and its relief (which, in the writer's 

 experience, is by no means invariable) with progesterone or 

 its analogues. 



Pregnancy 



In no physiological circumstances do such profound hor- 

 monal changes occur as in pregnancy. The output of oestrogens 

 rises some thousandfold, of progesterone ten to twentyfold, 

 and of adrenocortical and thyroid hormones to less impressive, 

 but still significantly increased levels. A new hormone, 

 chorionic gonadotrophin, found only in pregnancy, of foetal, 

 and therefore partly paternal origin — a "foreign protein", to 

 some extent — appears in the circulation immediately after 

 implantation, rises to striking levels by about the 60th day 

 of gestation and then as rapidly falls to about one-quarter 

 the maximum level during the remainder of pregnancy. The 

 sum total of these changes is to produce a substantial degree 

 of fluid and sodium retention in all pregnant patients. Oedema 

 is of course common; its association with hypertension, with 

 or without albuminuria to give pre-eclamptic toxaemia, is 

 also not uncommon. Toxaemia is, for the obstetrician, one 

 of the remaining major problems he has to face. Its patho- 

 genesis continues in obscurity, in spite of extensive research. 



Only one or two aspects of this vast problem will be dealt 

 with here. 



That water and sodium are retained in considerable 



