94 ESSENTIALS OF BACTERIOLOGY 



duce living cultures of bacteria into the bodies of animals 

 without their coming into direct contact with the tissues. 



Obtaining Material from Infected Animals. The ani- 

 mal should be skinned, or the hairs plucked out, before it is 

 washed at least the portion where the incision is to be made. 

 Then the entire body is washed in sublimate. Two sets of 

 instruments are required one for coarser and one for finer 

 work: the one sterilized in the flame; the other, to prevent 

 being damaged, heated in a hot-air oven. 



The animal, the mouse, for example, is stretched upon a 

 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 ex- 

 posed. 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 are first to be 

 looked at, they should be laid bare first. 



In this manner material is obtained and the results of 

 inoculation 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 ar- 

 tificial 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. 



