GROWTH AND CHEMICAL PURITY 283 



is made possible only through the work of the kinetic 

 system of the mother, aided, as the fetus develops, by 

 the kinetic system of the child. This much is certain, 

 that the growth of the fetus in the uterus is at a more 

 rapid rate than its growth after birth. 



A prematurely born infant, one delivered at six 

 months, which is kept at as even a temperature in 

 an incubator as in the uterus, does not show a rate of 

 growth equal to that of the fetus within the uterus. 

 The infant is now depending upon its own kinetic 

 system alone. That the kinetic systems of mother 

 and offspring work together is shown by the fact that 

 if the mother has a deficient thyroid gland, the new- 

 born babe may have a goiter, showing that the thyroid 

 of the fetus was called upon to supply the lack of 

 thyroid secretion, although whether this call was made 

 by the organism of the mother or of the fetus, or of 

 both, is not known. A possible evidence of the exces- 

 sive demand upon or of the deficiency of the adrenal 

 secretion is seen in the characteristic brownish discol- 

 oration of the skin of pregnant women. These discol- 

 orations are analogous to those of Addison's disease 

 and appear with pregnancy and disappear after de- 

 livery. 



At term, the phenomena of labor present interest- 

 ing examples of adaptive reactions. The preliminary 

 pain compels attention rest. The entire process, 

 from the warning pain to the muscular contractions and 

 muscular relaxations of delivery, is all an adaptation 

 to facilitate the birth. Birth opens an enormous 

 bleeding area. Vast blood vessels are rent asunder. 

 Large raw areas of uterine tissue are exposed to infec- 



