CHAPTER XIV 



H^EMOLYSINS AND ALLIED BODIES 



IF non-fatal amounts of certain bacteria, or of certain toxins 

 produced by bacterial growth, 1 be repeatedly inoculated into 

 susceptible animals, a day or so intervening between each 

 inoculation, it will be found that the animal acquires the power 

 of withstanding larger and larger doses, and ultimately can tolerate 

 an amount many times greater than that which would have 

 proved fatal before the inoculations began. These facts have 

 been known to bacteriologists for several years, the animal thus 

 treated being described as immunised against the bacteria or 

 toxins in question. It has further been shown that it is the 

 blood which acquires this immunising property, and that the 

 process can to a large extent be studied in vitro for example, 

 by mixing some immunised blood serum with a suspension of 

 bacteria and observing the bacteria under the microscope, or by 

 mixing the serum with some toxin, and then seeing whether the 

 mixture is still toxic when injected into a susceptible animal. 



These means of studying the antibacterial or antitoxic action 

 of serum require, however, patient observation, and the effect 

 produced can only be measured quantitatively by extremely 

 laborious methods. 



Within the last two or three years, however, it has been 

 .shown that substances which behave like bactericidal and antitoxic 

 bodies can be produced in the tissue fluids by the injection into 

 an animal of various cells other than bacteria, and poisons other 

 than those of bacterial origin. Included amongst the toxic cells 

 are the red blood-corpuscles of an animal belonging to a different 

 species to that from which the corpuscles are derived. The 

 destruction of the red corpuscles, or erythrocytes, is indicated by 



1 Bacterial toxins may be excreted (exotoxines) and pass in the blood to parts 

 of the body remote from the seat of inoculation, or the poisons may be closely 

 bound with the microbe (endotoxins) and be set free only after dissolution of 

 the microbe. The efforts of the host to combat the two forms of intoxication 

 are different in manner. (Editor's Note.) 



433 2E 



