OPSONIC TECHNIC 87 



board, a nail or pin through each leg, and the head fixed with 

 a pin through the nose. The skin is dissected away from the 

 belly without exposing the intestines. Then the ribs being 

 laid bare, the sternum is lifted up, and the pericardium exposed. 

 A platinum needle dipped into the heart after the pericardium 

 has been slit will give sufficient material for starting a culture. 

 If the other organs are to be examined, further dissection is 

 made. If the intestines were first to be looked at, they would 

 be laid bare first. 



In this manner material is obtained and the results of inocu- 

 lation noted. 



Frequent sterilization of the instruments is desirable. 



Koch's Rules in Regard to Bacterial Cause of Disease. 

 Before a microbe can be said to be the cause of a disease, it 

 must 



First, be found in the tissue or secretions of the animal suf- 

 fering from, or dead with, the disease. 



Second, it must be cultivated outside of the body on artificial 

 media. 



Third, a culture so obtained must produce the disease in 

 question when it is introduced into the body of a healthy animal. 



Fourth, the same germ must then again be found in the animal 

 so inoculated. 



CHAPTER XVI 

 OPSONIC TECHNIC 



Method of Counting Bacteria in a Culture. In the use 



of protective vaccines, a method of counting the bacteria in a 

 given amount of serum or emulsion has come into practice, 

 especially in the opsonic index treatment. 



First, the number of red cells in a cubic millimeter of blood 

 is measured; then, in a capillary tube (Wright pipet), blood 



