DISEASES OF SWINE 513 



ground oats and corn, or crushed wheat, and then stirring into 

 this the proper quantity of the medicine. 



After an outbreak of cholera the yards and pens should be thor- 

 oughly cleaned, all dead hogs should be burned, the litter should 

 be collected and burned, and quicklime scattered freely over the 

 ground. The houses should be washed thoroughly with a coal- 

 tar preparation before new stock is brought in. The troughs 

 should be burned, or if this is not practicable, they should be 

 thoroughly soaked in coal-tar preparation and then washed out. 

 The lots and houses should not be used again for some time. 



Prevention of cholera by immunization. — The Bureau of Ani- 

 mal Industry, Department of Agriculture, has developed a serum 

 which by means of vaccination will render hogs immune to chol- 

 era. While its preparation and use are attended with difficul- 

 ties, the method is briefly given here because of the feeling that 

 if it is to prove practicable, it. must be so simpUfied as to be used 

 by any careful workman. Furthermore, a drove of cholera hogs 

 affords a very good opportunity to practice, as their value is not 

 likely to be great, especially if the attack is virulent. 



In order to make the method clear it will be divided into two 

 main parts : the preparation of the serum, and the use of the 

 serum. 



Preparation of the serum. — To prepare the serum one must 

 first procure an immune hog with a long heavy tail, since it is 

 at this point that the serum is drawn, and it may be necessary 

 to clip the end two or three times in drawing the serum. This 

 may be a hog that has recovered from an attack of cholera, 

 as such animals are immune to further attacks, or it may be 

 one rendered immune by the method herein described. This 

 hog we will call the supply animal. This animal must now be 

 hyper-immunized. This consists of inoculating him, in the mus- 

 cles of the thigh, with about 10 c.c. (cubic centimeters) of 

 ■virulent hog cholera blood, from which the clot has been re- 

 moved by stirring or whipping with a clean stick, to the pound 

 2l 



