202 JOHN LEWIS BREMER 



In the case of man the question of the activity of the fetal 

 kidney has been much considered by anatomists and physiolo- 

 gists, and many conflicting reports are published pro and con. 

 The question is discussed by all those interested in the origin and 

 constitution of the amniotic fluid. That the fetal kidney in 

 man may be active just before birth is abundantly proved by 

 the numerous observations of immediate micturition in the new- 

 born, yet the small quantity passed in these cases and the ab- 

 sence of any great amount of the urinary constituents in the 

 accompanying amniotic fluid show that the renal activity has 

 not been of long duration. Ahlfeld and English demonstrate, 

 by their cases of total absence of the fetal kidneys and of the 

 blocking of the fetal urinary passages, already referred to, that 

 the kidney is not a necessity before birth; on the other hand, 

 cases of fetal hydronephrosis, of fetal calculi, and the occasional 

 presence of large amounts of urinary matter in the amniotic 

 fluid, all point to a prolonged renal activity. Preyer reviews 

 the various statements and comes to the conclusion that the 

 real cause of the inactivity of the fetal kidney is probably the 

 low blood pressure of the fetus, and in proof of this contention 

 quotes from Schatz a case of twins with separate amniotic cavi- 

 ties. One, which had an enormous amount of amniotic fluid, 

 urinated a great quantity and almost hourly during the six hours 

 of its life; the other, which had very little amniotic fluid, passed 

 no urine in twelve hours. The kidneys and heart of the first 

 weighed one and a half times as much as those of the second. The 

 first had a much higher blood pressure, "liefert niehr Harn und 

 dadurch mehr Fruchtwasser."'^ Whether the fetal blood pres- 

 sure of the pig, sheep, and cat, animals in which the fetal kid- 

 ney is active, is relatively higher than that of rodents and man, 

 in which it is not, I do not know; nor is it easy to understand 

 the rise of fetal blood pressure within the placenta of rodents and 

 man, to cause excretion there, which this explanation seems to 

 call for. 



Various experiments, quoted by AVertheimei', on rabbits and 

 guinea pigs near term or in the latter part of pregnancy prove 



^ Preyer, loc. cit., p. .333. 



