1.— PHYSIOLOGY. 183 



This fluid he injected subsequently into ten women with deficient labour 

 pains. In eight of the women pains were induced, which in four were 

 followed by the birth of the child. In another case an intradural injection 

 was made, which was followed by labour pains within twenty-four hours. 

 Mayer states that the cerebro-spinal fluid contains the active principle 

 of the pituitary responsible for the production of uterine contraction. 

 Siegert found that pituitrin, which is normally present in the cerebro- 

 spinal fluid, diminished in the later months of gestation. 



The interaction of bile salts and pituitary secretion is antagonistic on 

 the uterus. Hofbauer shows that there is a steady increase in the bile 

 salts in the blood of pregnant women as gestation proceeds. He thinks 

 that this factor is responsible for the control of the pituitary secretion 

 during pregnancy and that toward the end of labour the pituitrin action 

 overshadows the bile-salt action so that labour occurs. 



All these experiments consistently support the view that in the 

 presence of fully formed corpora lutea the normal ovarian secretion is 

 held in abeyance, and this is the condition for a short part of the time 

 between the heat periods, but more particularly during pregnancy. At 

 the close of pregnancy, when the corpora lutea are in an advanced stage 

 of involution, the normal secretory activity recurs and the pituitary 

 gland is excited to secrete more actively. When the threshold stimulus 

 of the pituitrin on the uterus is reached the pains of labour set in and 

 parturition results. The well-known phenomenon of the growing irrita- 

 bility of the uterus in the later stages of pregnancy, which is the typical 

 effect of the pituitary action, is explained as being functionally correlated 

 with the involution of the corpus luteum. 



It is not suggested that the ovario-pituitary endocrine mechanism is 

 the sole factor in producing labour pains. No doubt the foetus itself acts 

 as a direct stimulus, and without the foetus the intense muscular con- 

 tractions would not occur, but it is also clear that the onset of labour 

 cannot easily be accounted for without postulating some further exciting 

 cause apart from the foetus and the uterus. 



In conclusion, no romance can be more remarkable than the fact that 

 doctors, by using pituitary extract to stimulate the uterus in pregnancy, 

 should have adopted the method which Nature herself employs and that 

 physiological function is after all a pharmacological action. 



Concluding Remarks. 



Civilisation has been responsible for many new diseases. Our food- 

 stuffs in great cities are often preserved and important constituents of 

 fresh foods may be lacking. The science of dietetics has assumed an 

 enhanced importance lately, which is partly due to the artificial prepara- 

 tion of many of our foods. Many experiments have been made in my 

 laboratory to show that certain foods given in excess to animals fed on a 

 synthetic diet, but containing an ample supply of the recognised vitamins, 

 suffer from poisoning sometimes of the most profound and fatal kind. 

 The same experiments made on animals living on an ordinary diet show 

 that the excess of the ' poisonous ' food is harmless. For example, 

 certain preparations of irradiated ergosterol given to rats which are being 



