334 EXPERIMENTAL INOCULATION OF ANIMALS 



the microbe subsequently to the occurrence of that 

 diffusion. 



At the moment, however, our attention is directed 

 to the first of these broad headings, for it is by the 

 application of the knowledge acquired in its pursuit 

 that we are able to deal with problems arising under 

 any of the remainder. 



For whatever purpose the inoculation is performed, 

 it is essential that the experiment should be planned to 

 secure the maximum amount of information and the 

 minimum of discomfort to the animal used. Every 

 care therefore must be taken to ensure that the virus is 

 introduced into the exact tissue or organ selected ; and 

 the operation itself must be carried out with skill and 

 expedition, and under strictly aseptic conditions. 



In the course of inoculation studies many instances of 

 natural immunity, both racial and individual, will be 

 met with; but it must be recollected that natural im- 

 munity is relative only and never absolute, and care 

 be taken not to label an organism as non-pathogenic 

 until many different methods of inoculation have been 

 performed upon different species of animals, combined 

 when necessary with various procedures calculated to 

 overcome any apparent immunity, and have invariably 

 given negative results. 



In some countries experiments upon animals are 

 only permitted under direct license from the Govern- 

 ment, and then only within premises specially licensed 

 for the purpose. In England this license is in the 

 grant of the Home Secretary, and confers the permis- 

 sion to experiment upon animals under general anaes- 

 thesia, provided that after the experiment is completed 

 the animal must be destroyed before regaining con- 

 sciousness. If it is intended to carry out simple 

 hypodermic inoculations and superficial venesections, 

 Certificate A, granting this specific permission and 

 dispensing with the necessity for general anaesthesia 



