336 



Journal of Agricultural Research 



Vol. VI, No. 9 



CentripugaIvIzing. — The defibrinated blood mixture is placed in suit- 

 able containers, preferably some what elongated, and rotated in a centrifuge 

 for 15 minutes at a speed sufficient to produce in the cups a precipitating 

 force equal to approximately i ,700 times gravity. At the end of this 

 period the serum may be poured from the cups into suitable containers. 



Heating the serum. — The clear serum obtained by centrifugalizing is 

 placed in a container v^^hich is surrounded by a jacket of v^^ater. The 

 temperature of the water in the outer jacket at the beginning of the 

 heating should not exceed 63° C. The serum in the inner container 

 is slowly stirred during the heating process, the temperature of the 

 outer jacket being maintained between 6i° and 62°. A thermometer 

 should be kept constantly in the serum and care should be taken to 

 see that the temperature of the serum, once it has reached 60° C, does 

 not fall below that point and that it does not rise materially above it.^ 

 Continuous heating for 30 minutes at 60° C. is required. Upon the com- 

 pletion of the heating, the serum should be rapidly cooled. After cooling, 

 I part of a 5 per cent solution of phenol should be added to 9 parts of 

 the serum. 



Filtering the serum. — After the phenol has been added a slight 

 precipitate may at times form in the serum; therefore it is desirable to 

 allow several days to elapse between the addition of the phenol and the 

 final filtration through infusorial earth. 



EXPERIMENTAL RESULTS 



To illustrate the yield of clear serum obtained by the application of the 

 described method to the preparation of anti-hog-cholera serum, there 

 is given in Table I a statement of the yield of clear serum obtained from 

 three different lots of defibrinated immune blood and one lot of defibri- 

 nated hog-cholera virus. 



Table I. — Yield of clear seruvi from defibrinated anti-hog-cholera serum and virus 

 under a precipitating force of 1,700 tim,es gravity applied for 12 minutes 



Blood. 



Serum 

 yield. 



Hog-cholera serum from defibrinated immune blood 3895 . 



Do 



Do 



Do 



Serum from defibrinated immvme blood 3866 and 2165 



Serum from defibrinated immune blood 2166 



Serum from defibrinated hog-cholera virus 377 and 379. . . 



Per cent. 

 47J4 

 49 

 70 

 70 

 74 

 70 



Table II gives the results of potency tests of one lot of serum prepared 

 by use of the bean and sodium chlorid mixture. As will be seen, a test 

 was made of the whole defibrinated blood, of the clear serum separated 



1 Thermometers used should be standardized, and the temperature of the serum should not be allowed 

 to exceed 60.5° C. 



