228 GENERAL THERAPEUTICS FOR VETERINARIANS 



1. The serum theory of von Behring locates the immunizing 

 substances in the cell-free blood-serum. Under the influence of 

 the pathogenic microorganisms the body cells produce chemical 

 substances with disinfectant properties (antibodies, alexins, im- 

 mune proteins) which destroy the bacteria (bactericidal action) 

 either by dissolving (bacteriolysins), clumping (agglutinins), or 

 precipitating (precipitins) them, or which neutralize their toxins 

 (antitoxins) or facilitate phagocytosis (opsonins). Artificially 

 inoculating the antitoxins in the form of the blood-serum of 

 immune animals into healthy animals produces in the latter 

 passive immunity; if the material is injected into diseased animals 

 recovery occurs (von Behrmg's law; serum therapy). These anti- 

 toxins have not up to this time been isolated in their pure state. 

 According to von Behring, this is not possible principally because 

 they are not an antitoxin material but an antitoxic force similar 

 to the magnetic force of iron (!). Von Behring has differentiated 

 in vaccination the isotherapeutic (inoculation of the bacteria 

 themselves, Jennerization, cow pox vaccination, vaccination 

 against tuberculosis of cattle) and the homceotherapeutic principle 

 (inoculation of the specific serum in diphtheria, swine erysipelas, 

 tetanus) (see p. 22). 



Modifications of the serum theory have been formulated by 

 Buchner, Ehrlich, Brieger, Emmerlich, Wassermann, Lorenz, and 

 others. According to Buchner, the antitoxic body is an enzyme 

 with a ferment-like action 



2. The phagocytic theory of Metschnikoff is, on the contrary, 

 a cellular theory, which places the immunizing force in the white 

 blood-cells (leucocytes, phagocytes). In infectious diseases, these 

 cells remove the invading infectious agents and their pathogenic 

 products from the blood by taking them within the cell body 

 (leucocytosis, phagocytosis). In local infection (inflammation), 

 they leave the blood-vessels in the form of wandering cells or pus 

 cells in order to take up the infectious material (positive chemo- 

 tropism or positive chemotaxis). In addition to this higher sus- 

 ceptibility of the cells, there also occurs through adaptation an 



