REPRODUCTION 1017 



as that of the blood, and although a portion of the amniotic fluid, 

 which contains traces of urea and salts, in addition to small quantities 

 of albumin, may be secreted by the renal tubules, and find its way 

 through the still open urachus into the amniotic sac, this contribution 

 cannot imply more than a slight degree of glandular action. Under 

 certain experimental conditions, however, it can be largely increased. 

 Thus, extirpation of the kidneys in a pregnant animal causes an 

 inciease in the amount of amniotic fluid (hydramnios) through the 

 stimulation of the foetal kidneys to increased activity by the passage 

 of the unexcreted urinary constituents of the mother's blood into 

 that of the fetus. After the injection of phloridzin into the foetus 

 sugar has been found in abundance in the amniotic fluid, although 

 the injection of that drug into the mother caused no such effect. On 

 the other hand, after injection of sodium sulphindigotate into the 

 circulation of the foetus in the sheep, the foetal kidneys contained 

 particles of the pigment, while the amniotic fluid remained un- 

 coloured. Long before full term the sebaceous glands have begun 

 their work by the secretion of the vernix caseosa, an oily material 

 which covers the skin and serves to protect it from the continual 

 irritation of the fluid in which the embryo floats. 



The nervous system is even less active than the glandular tissues, 

 and not more active than the muscles. There is evidently no scope 

 for the exercise of the special senses. Psychical activity of every 

 kind must be at its lowest ebb. Consciousness, if it exists at all, 

 must be dull and muffled. And if motor impulses are discharged 

 from the cortex, the psychical accompaniments of such discharge are 

 doubtless widely different from those which we associate with 

 voluntary effort. 



It is a remarkable fact that this functional calm, broken only by 

 the beat of the heart, is accompanied by a relatively intense 

 metabolism of the same order of magnitude as that of the adult. 

 In the hen's egg at all stages of development the consumption of 

 oxygen and production of heat (per kilogramme and hour) are the 

 same as in the adult hen. The oxygen consumption and carbon 

 dioxide production of pregnant guinea-pigs were determined before 

 and during compression of the umbilical cord of a foetus, and a distinct 

 diminution was observed, when the respiratory exchange of the foetus 

 was eliminated. From the results of a number of observations it 

 was calculated that the carbon dioxide produced by the mother 

 was 462 c.c., and by the foetus 509 c.c. per kilogramme of body- 

 weight per hour (Bohr and Hasselbach). A similar comparison 

 between women before and during pregnancy never showed any 

 diminution in the respiratory exchange reckoned on the unit of body- 

 weight in the pregnant condition. In one case, indeed, and that 

 the most exactly observed, there was an increase in pregnancy. 

 Now, in the pregnant woman a considerable part of the increase of 

 body-weight is due to the amniotic fluid, in which, of course, meta- 

 bolism does not go on. It is evident, then, that in the human foetus 

 also the intensity of metabolism is at any rate not of a lesser order of 

 magnitude than in the mother, in spite of the much smaller amount 

 of muscular contraction taking place. The heat production of mother 

 and child together has been directly estimated in several cases in a 

 respiration calorimeter provided with a bed just before parturition 

 and just after it. After parturition the heat production of the 

 mother was also separately determined. From the difference it was 

 concluded that the heat production of the child per kilogramme of 



