2GO SUSCEPTIBILITY AND IMMUNITY. 



oculation into susceptible animals, neutralizes the pathogenic power 

 of these cultures. 



They have shown by experiment that the blood of a rabbit which 

 has an acquired immunity against tetanus, mixed with the virulent 

 filtrate from a culture of the tetanus bacillus, neutralizes its toxic 

 power. One cubic centimetre of this filtrate was mixed with five 

 cubic centimetres of serum from the blood of an immune rabbit and 

 allowed to stand for twenty-four hours ; 0. 2 cubic centimetre of this 

 injected into a mouse was without effect, while 0.0001 cubic centi- 

 metre of the filtrate without such admixture was infallibly fatal to 

 mice. The mice inoculated with this mixture remained immune for 

 forty to fifty days, after which they gradually lost their immunity. 

 The blood or serum from an immune rabbit, when preserved in a 

 dark, cool place, retained its power of neutralizing the tetanus tox- 

 albumin for about a week, after which time it gradually lost this 

 power. The blood of chickens, which have a natural immunity 

 against tetanus, was found not to have a similar power. Behring 

 and Kitasato have also shown that the serum of a diphtheria-immune 

 rabbit destroys the potent toxalbumin in diphtheria cultures. It 

 does not, however, possess any germicidal power against the diph- 

 theria bacillus. 



Ogata, in 1891, reported that he had succeeded in isolating from the 

 blood of dogs and of chickens a substance to which he ascribes the nat- 

 ural immunity of these animals from certain infectious diseases, and 

 the power of their blood to protect susceptible animals from the same 

 diseases. This substance is soluble in water and in glycerin, but in- 

 soluble in alcohol or ether, by which it is precipitated without being 

 destroyed. Its activity is neutralized by acids, but not by weak 

 alkaline solutions. Ogata supposes the substance isolated by him to 

 be the active agent in blood serum by which certain pathogenic bac- 

 teria are destroyed, as shown by the experiments of Nuttall, Buchner, 

 and others. Hankin had previously isolated an albuminoid sub- 

 stance from the spleen and blood of the rat, to which he ascribed the 

 immunity of this animal from anthrax. This substance, according 

 to the author named, is a globulin; it is insoluble in alcohol and in 

 distilled water, and does not dialyze. 



Tizzoni and Cattani ascribe the protection of animals which have 

 acquired, an immunity against tetanus to the presence of an albumi- 

 nous substance which they call the tetanus-antitoxin. This they 

 have isolated from the blood of immune animals. They arrive at 

 the conclusion that it is a globulin, or a substance which is carried 

 down with the globulin precipitate, and that it is different from the 

 globulin, above referred to, obtained by Hankin from animals im- 

 mune against anthrax. 



