Originally published in Acta Physiol. Scand. 1, 11 (1940) 



43. RATE OF PASSAGE OF WATER THROUGH 

 CAPH^LARY AND CELL WALLS 



O. Hevesy and C. F. Jacobsen. 



Institute of Theoretical Physios and the Carlsberg Laboratorj^ Copenhagen 



Water molecules, which are absorbed into the circulation, will mix 

 rapidly with those present in the plasma. They will then penetrate the 

 capillary wall and become distributed in the extracellular fluid. Ulti- 

 mately, they will invade the cells. Simultaneously, a loss of some of the 

 water molecules through the kidneys, the bowels, the lungs and through 

 peripheral evaporation will also take place. It is difficult to estimate 

 even very roughly the rate at which some of the above processes take 

 place. Experiments in which heavy water is used as an indicator permit, 

 however, the determination of the rate at which individual water mole- 

 cules introduced into the circulation are distributed in the body water 

 and from these determinations to answer the above questions. 



We inject a few cc. of practically pure heavy water into the jugularis 

 of a rabbit and take at intervals blood samples from the carotis. The 

 next step is to prepare pure water from the blood samples^^) and to 

 determine ist density. Let us assume that we inject 1 cc. of heavy water 

 having a density of 1.1000, and find for the water prepared from a 

 blood sample the value 1.001. Then we must conclude that the 1 cc. 

 heavy water injected into the vein w^as diluted by 99 cc. of normal 

 water present in the body of the rabbit in the course of the time which 

 elapsed between the injection of the heavy water and the collection 

 of the blood sample. 



EXPERIMENTAL PROCEDURE 



Heavy water in contact with air containing vapour of normal water rapidly 

 becomes hghter in consequence of the interchange in the vapour phase. In view 

 of this interchange, it was necessary to keep the samples containing heavy water 

 out of contact with the moist atmosphere. The blood samples of about 1 cc. 



(i)The total water content of the blood has to be distilled to avoid a fractiona- 

 tion of the diluted heavy water, the vapour pressure of deuterium oxyde being 

 smaller than that of HjO. 



