ADVENTURES IX KADIOISOTOPE llESEARCH 519 



vity of the samples is facilitated if they have practically the same weight 

 and it is for this reason that we added to the original sample a compara- 

 tively large amount of non-active phosphate. The corpuscles of 1 cc. 

 of the blood of rabbit B were also extracted with ether-alcohol and the 

 extract treated in the way described above. The activity of the sample 

 thus obtained, was then compared with that of the corresponding sample 

 of rabbit A. 



Let us denote the injected blood volume by Vj, the volume of the 

 sample collected for analysis from rabbit B and rabbit A, respectively, 

 by Vj and Vjj, and the activity of the two samples obtained by Aj and 

 Ajj; then the blood volume to be determined (X) becomes 



^^A,.V...V, 



A„.V, 



In some of our experiments, before injecting, for example, 1 cc. 

 blood into the jugularis of rabbit A, we removed 1 cc. In that case, the 

 second term of the equation becomes O. 



Operations involved in the determination of the total blood volume 

 are thus: measurement of the volume of three samples, and the compa- 

 rison of the radioactivity of two samples. 



In the above mentioned experiment the corpuscle phosphatides of 

 1 cc. blood of rabbit B contained 100 relative activity units; the activity 

 of the corpuscle phosphatides extracted from 50 cc. blood of rabbit A 

 was found to be 53.3. From these values it follows that the blood volume 

 of rabbit B amounts to 93.8—1 cc. = 92.8. 



b) Making use of labelled acid-soluble compounds of the corpuscles 



We can check the result obtained above by another procedure in which, 

 instead of the labelled phosphatides, the labelled acid-soluble phosphorus 

 compounds are involved. After extraction of the phosphatides, the cor- 

 puscles are extracted with 10 per cent trichloroacetic acid. The P of the 

 filtrate obtained is converted, as described above, into ammonium 

 magnesium phosphate. The activity of the sample obtained from rabbit 

 A is compared with that of the sample from rabbit B, as described above. 

 The figures obtained being 100 and 54.4 respectively, the total blood 

 volume of rabbit A becomes 



Aii-Vi 54.4-1 



The use of labelled acid-soluble P compounds leads thus to practically 

 the same result as obtained with labelled phosphatides as indicators. 



The blood volume per kgm of rabbit weight was found, in the experi- 

 ment described above, to be 46 cc. In another experiment the value 

 of 38 cc. was found. 



