46 INFECTION AND RESISTANCE 



tissue which is independent of accidental factors and seems to be 

 due to specific chemical or physical affinity. It seems even that in 

 tetanus, botulismus, and a few other conditions there is a differential 

 selection of particular areas within a tissue like the nervous system, 

 just as this occurs in the case of certain drugs. As stated above we 

 have no satisfactory scientific explanation for this, but a great deal 

 of work has been done to show that the bacterial poisons actually 

 unite with and are taken up by the susceptible tissues. 



Indirectly, proof of this has been brought by the demonstration 

 of the rapid disappearance of various toxins from the blood streams 

 of susceptible animals and their persistence in the circulation of 

 animals insusceptible to them. Thus Donitz 53 has shown that 

 tetanus toxin injected into the blood stream of a susceptible animal 

 rapidly diminishes in quantity, and Knorr, 54 in similar experiments, 

 showed that the demonstrable disappearance of such toxins out of 

 the blood stream is synchronous with the appearance of symptoms, a 

 fact which excludes disappearance by excretion. Conversely Asa- 

 kawa 55 showed that in pigeons, which are but slightly susceptible, 

 tetanus poison could be demonstrated in blood, liver, spleen, kidneys, 

 and muscles six days after injection, but not in the brain, showing 

 that in this organ, at least, there must have been either a union or a 

 destruction of the poison. Similar to these results are those of 

 Metchnikoff, 56 who found the poison unchanged after two months in 

 the circulation of insusceptible animals (lizards). 



Direct evidence of union between susceptible tissues and poison 

 has been furnished by the experiments of Wassermann and Takaki, 57 

 who showed that the brain and cord tissues of rabbits and guinea 

 pigs, mixed with tetanus toxin before injection, served to neutralize 

 its harmful effects. And it appears that the toxin-neutralizing prop- 

 erty of the brain substances of various animals is proportionate to 

 their individual susceptibility to the poison. Thus Metchnikoff 58 

 not only confirmed the results of Wassermann and Takaki for rab- 

 bits and guinea pigs, but showed further that the brains of chickens, 

 animals that are but moderately susceptible, possess a correspond- 

 ingly slighter neutralizing power, and, further, that brain tissues of 

 entirely insusceptible cold-blooded animals, turtles and frogs, pos- 

 sess absolutely no neutralizing properties. 



The original interpretation by Wassermann of these facts was 

 based on the assumption that the poison was bound to the brain tissue 



53 Donitz. Deutsche med. Woch., No. 27, 1897. 



54 Knorr. Fortschr. der Medizin, 1897, No. 17, and Munch, med. Woch., 

 1898, Nos. 11 and 12. 



55 Asakawa. Centralbl. f. Bakt., Vol. 24, pp. 166 and 234. 



56 Metchnikoff. "L'lmmunite dans les maladies Infect.," Paris. 



57 Wassermann and Takaki. Berl. Uin. Woch., 1898, No. 1. 

 ss Metchnikoff. Ann. de I'Inst. Past., 1898, p. 81. 



