Abstract
The concentrations of sodium, potassium, chloride and creatinine in allantoic fluid have been investigated in normal cows and in cases of hydrallantois. After three months of pregnancy the ion concentrations in normal allantoic fluid lost their initial resemblance to extracellular fluid. During pregnancy the concentrations of creatinine in allantoic fluid increased, and after about three months the increase became slower but exponential with time. The excretion-reabsorption mechanisms responsible for the characteristics of the allantoic fluid the last 6 months of normal pregnancy appear to be altered or ineffective in cases of hydrallantois. The sodium, potassium, and chloride concentrations contrary to normal conditions resemble extracellular concentrations, and the creatinine concentrations were much lower than normal. In hydrallantois a structural or functional change of chorioallantois seems to be present although a dysfunction of the foetal kidney cannot be excluded. The problem requires further investigation of ion transport and permeability across the chorio-allantoic membranes.