Interrelation of Plant and Animal Pathology 63 



other bodies exist in an immune serum, which are able to throw 

 bacteria into clumps or adherent groups and render them harmless. 

 These are called agglutinins. Another class of anti-bodies has been 

 recognized in immune sera, which will precipitate homologous bac- 

 terial extracts and are called precipitins. 



In some of the pathogenic bacteria the poisons constantly diffuse 

 out into the medium. The diphtheria bacillus is a prominent rep- 

 resentative of this class. Bacterial poisons of this kind are known 

 as exotoxins. 



In other cases, as in the cholera spirillum, the toxins are locked 

 up within the body of the parasite and do not escape into the serum 

 or medium until it dies. These are known as endotoxins. 



Immunity may be acquired in several ways. The actual organ- 

 isms in an attenuated form, or their toxins, may be injected into 

 the blood of the patient. This causes the serum to respond by the 

 formation of the specific anti-bodies, which thus render the patient 

 immune. Or antibodies may be provoked in the serum of another 

 animal as is done with the horse in the case of diphtheria, the serum 

 from this animal then contains the antibodies and becomes an anti- 

 toxin, which may be used successfully in the treatment of the disease 

 in question. It is very significant also that specific antibodies may 

 be formed in the serum from the injection of minute doses of snake 

 venom and of a number of other poisons, generally protein com- 

 pounds. For the purposes of our discussion it is very significant 

 that the symptoms of a disease are provoked by injections of the 

 poisonous products of the causative organisms. 



The question of the production of specific antibodies by plants 

 has scarcely been touched upon by plant pathologists. The difficul- 

 ties in the way of such investigations are readily apparent. There 

 is no such thing as a "humoral fluid" in the plant body comparable 

 to the blood serum of the higher animals, and if such reactions 

 actually occur in plants the antibodies must be sought in the sap 

 of individual cells. As a matter of fact, a young Austrian patholo- 

 gist, R. J. Wagner, reported the discovery of antibodies in the po- 

 tato, late in 1914. He records the occurrence of — 



"1 — Agglutinins, that is, bodies which retard flagellate move- 

 ment." 



"2 — Lysins, which cause the cell walls of the bacteria to swell up 

 and to pass into solution." 



