SUMMARY OF SERUM MANUFACTURE 361 



nal method). The most successful of these methods is the intra- 

 venous. 



(9) One week after this hyperimmunization the animal is bled 

 for the purpose of obtaining serum blood. This bleeding is per- 

 formed by cUpping off the end of the tail and allowing the blood to 

 flow. 



(10) The amount of blood drawn should be 5 c.c. for each pound 

 of body weight. 



(11) These bleedings are repeated at intervals of one week for 

 three bleedings. 



(12) One week after the third tail bleeding the hog is again 

 injected with a dose of virus blood. At this time there is again 

 injected 5 c.c. of virus per pound of body weight. 



(13) One week after this rehyperimmunization the hog is again 

 ready to bleed. 



(14) The bleedings are now made from the tail at intervals of 

 one week. 



(15) At the end of the third week the animal is given a final 

 bleeding and slaughtered. The blood at this time is drawn from 

 the large vessels of the neck, as in the case of the virus pigs. 



(16) This blood obtained from the tail bleedings is placed in 

 shaking or defibrinating machines just as soon as drawn, and vigor- 

 ously stirred or shaken until all the clot is separated from the fluid 

 of the blood. This is now filtered through cotton or gauze and is 

 the so-called serum. 



(17) Hog-cholera serum is, in reality, not a serum, but a de- 

 fibrinated blood. 



(18) One hundred c.c. of 5 per cent, carbohc acid solution is 

 now added to each 900 c.c. of serum, to act as a preservative 

 agent. 



(19) The serum is now bottled and kept in a cool, dark place 

 until ready for use. 



Centrifuged Serum. — The hog-cholera serum, as just described 

 above, is a dark-colored liquid of most unpleasing appearance. 

 This is due to the presence in it of the large number of red blood- 

 corpuscles or cells. In some serum plants in this country an effort 

 is being made to overcome this objection by removing the red blood- 

 cells. In the serum plant in Hungary this is being done, and the 



