440 



ADVENTURES IN RADIOISOTOPE RESEARCH 



a solution of heavy water into the jejunal loops of rats and investigated the heavy 

 water content of the intestinal fluid of the rats killed 1 hour after the start of the 

 experiment. They found the diluting water volume of the rat to amount to 66 per 

 cent of the body weight. 



Experiment B 



This experiment was carried out on a rabbit weighing 1.5 kgm 5.0 cc. of heavy 

 water were injected. The injection took 6 sec. The first blood sample was taken 

 in the interval of 22—26 sec. after the start of the experiment. The time recorded 

 is reckoned from the moment that half of the heavy water was injected until 

 half of the blood sample was collected. 



While rabbit A had not shown any sign of distress after the blood samples 

 were taken, this was not the case with rabbit B. In the course of the two days 

 following the start of the experiment, only a small amount of urine was produced 

 by rabbit B, with the consequence that no pronounced effect due to loss of heavy 

 water through the kidneys is shown by the density figures of the blood water 

 sample of rabbit B, collected after the lapse of 2 days, in contradistinction to the 

 results obtained when investigating the blood water of rabbit A after the lapse 

 of some days. 



DISCUSSION 



We found that, within about 1/2 min, heavy water injected into the 

 jugularis of rabbits was diluted by a large amount of body water, the 

 volume of which corresponds to about that of the extracellular space 

 of the body. This rapid dilution is followed by a second, slower process, 

 presumably due mainly to a further dilution of the heavy water by 

 cellular body water. From these findings it follows that all w^ater mole- 

 cules present in the plasma pass with a very high speed through the 

 capillary walls and with a slower, but still remarkable speed through 



