152 PRINCIPLES OF VETERINARY SURGERY 



have these facts been known concerning infectious diseases, 

 but similar facts have been demonstrated of snake-venom, 

 protozoan diseases, and a few^ vegetable poisons, al^rin, ricin, 

 etc. However, it is only during the last few years that im- 

 munity has made such wonderful strides, and has now 

 reached the stage of so great practicability. This is due 

 largely to the work of such men as Pasteur, Buchner, Met- 

 chnikoff, Behring, Koch, Chaveau, Bordet, Wasserman, 

 Ehrlich, Nuttall, Wright, and many others. Due credit 

 must also be given to the various pharmaceutical houses, 

 Parke Davis, Frederick Sterns, Mulford and the Pasteur 

 Vaccine Company. These commercial plants have greatly 

 simplified the practical application of immune sera. Prob- 

 ably no other branch of science is being investigated at 

 this time in different parts of the world with such enthus- 

 iasm as the various aspects of immunity. In all the govern- 

 ment laboratories, this work is being pushed, and many 

 philanthropists have made large gifts to further this work. 

 Finally, immunity in its dififerent phases has more to offer 

 to the investigator than any other branch of veterinary 

 medicine. We are looking forward to the time that for 

 every infectious disease we shall have an antitoxin, and, 

 better still, a preventive. 



TYPES OF IMMUNITY. 



The following outline will aid in classifying the various 

 forms of immunity which may occur: 

 Immunity — Antitoxic or Antibacterial. 



1. Natural — Inherited by species, families, or individ- 

 uals. 



2. Acquired 



a. Artificial 



Active, as in vaccination. 

 Passive, as in antitoxin injection. 



