476 IMMUNITY. 



for example, that the amount of antitoxin produced by an animal 

 may be many times greater than the equivalent of toxin injected ; 

 and further, that when an animal is bled the total amount of 

 antitoxin in the blood may some time afterwards be greater than 

 it was immediately after the bleeding, even although no addi- 

 tional toxin is introduced. This latter circumstance shows 

 antitoxin is formed by the cells of the body. If antitoxin is a 

 product of the cells of the body, we are almost compelled, on 

 theoretical grounds, to conclude that it is not a newly manufac- 

 tured substance, but a normal constituent of the living cells 

 which is produced in increased quantity. We have, however, 

 direct evidence of the presence of antitoxin under normal con- 

 ditions, — the presence of such being shown by its uniting with 

 toxin and rendering it inert. Normal horse serum, to mention 

 an example, may have a varying amount of antitoxic action to 

 the diphtheria poison, ox-bile has a similar action to snake poison, 

 whilst in the case of other anti-substances — such as agglutinins, 

 bacteriolysins, hasmolysins, etc. — whose production is governed 

 by' the same laws, numerous examples might be given. It is, 

 however, rather to the protoplasm of living cells than to the serum 

 that we must look for evidence of antitoxins. In the first place, 

 we have evidence that in the living body bacterial toxins enter 

 into combination with, or, as it is often expressed, are fixed by 

 the tissues — presumably by means of certain combining affinities. 

 This has been shown by the experiments of Donitz and of Hey- 

 mans with tetanus toxin. We have, however, no evidence as to 

 where the toxin is fixed in such cases beyond that supplied by the 

 occurrence of symptoms. Another line of research which has 

 been followed is to bring emulsions of various organs into con- 

 tact with a given toxin and observe whether any of the toxicity 

 is removed. This was first carried out by Wassermann and 

 Takaki, who investigated the action of emulsions of the central 

 nervous system of the susceptible guinea-pig on tetanus toxin. 

 They found in this way that the nervous system contained bodies 

 which had a neutralising effect on the toxin. For example, it 

 was shown that i c.c. of emulsion of brain and spinal cord was 

 capable of protecting a mouse against ten times the fatal dose 

 of toxin. These observations have been confirmed, though their 

 significance has been variously interpreted. It would, however, 

 be out of place to discuss at length the opposing views, and we 



