THE SOURCE OF THE AMNIOTIC AND ALLANTOIC FLUIDS IN MAMMALS. 



99 



the higher molecular concentration found both by Jacque and Grunbaum (fig. 1), of the 

 amniotic fluid early in pregnancy might cause an osmosis of water from the allantoic to 

 the amniotic sac (fig. 3). This might account for a concentration of the allantoic fluid 

 and the rise in the sp. gr. and in the non-protein nitrogen ; and, if the amniotic fluid 



BLOOD 

 AMNIOTIC 



ALLANTOIC 



JACQUE 



BLOOD 

 AMNIOTIC 

 ALLANTOIC 



CRUNBAUM 



Fig. 1. — To show changes in the molecular concentration of the fluids throughout gestation. 



were also being added to from the kidneys, it might explain the slight change in the 

 sp. gr. and in the non-protein nitrogen in the amniotic fluid. 



On the other hand, diffusion might explain the passage of sugar and of the nitrogen 

 in the form of readily diffusible urea from the allantoic to the amniotic fluid, thus 



Allantois Amnion 



Foetal Bladder 



osmosis 



HiO. 



Fig. 3. 



— Amount 

 -,- Sp. C. 



■-- Hon- protein N: 



— Sugar 



Fig. 2. 



raising the percentage of sugar in the amnion and maintaining the percentage of 

 non-protein nitrogen (fig. 3). 



The absence of further increase in the amniotic fluid in the later stages of pregnancy 

 may be due partly to the foetus swallowing the fluid, and, in the cow at least, passing it 

 into the allantoic sac ; but it may in part be due to the rise in the molecular concentration 

 of the allantoic fluid (Jacque and Grunbaum) arresting the osmotic stream. This would 



