PRINCIPLES OF BACTERIOLOGY 



During the investigations on the bactericidal substances of the blood 

 the discovery of the antitoxins was made by Behring and Kitasato, and 

 the nature of toxins was investigated by Roux, Ehrlich, and others. 



Ehrlich's Theories. Ehrlich 's researches led to the development of 

 his theories on immunity which have had a powerful influence upon 

 all later investigations in this field. His pupil and colleague, Wasser- 

 mann, explains them in the following words: 



Ehrlich began by observing that of the many poisonous substances 

 known to us only a comparatively small number existed against which 

 we could truly immunize i. e., obtain specific antibodies in the blood 

 serum of the immunized organism. Let us look at two poisons which 

 are very similar in their physiological action, for example, strychnine 

 and tetanus poison, both of which excite spasms through the central 

 nervous system. It is really curious that the injection of one, strych- 

 nine, produces no antibody whatever in the serum, while the injection 

 of the other, the tetanus poison, causes the formation of the specific 

 tetanus antitoxin. Ehrlich says that this is because these substances 

 enter into entirely different relations with the cells of the living organ- 

 ism. The one substance, strychnine, merely enters into a loose com- 

 bination with the cells of the central nervous system, so that it can again 

 be abstracted from these cells by all kinds of solvents e. g., by shaking 

 with ether or chloroform. The combination, therefore, is a kind of 

 solid solution, such as has been shown for the staining with aniline 

 dyes. The tetanus poison, on the contrary, Ehrlich says, is firmly 

 bound to the cell; it enters the cell itself, becoming a chemical part of 

 the same, so that it cannot again be abstracted from the cell by solvent 

 agents. He compares this process to .the assimilation of nutrient sub- 

 stances. Hence the difference between these two substances could be 

 likened to that between saccharin and sugar. Both substances taste 

 sweet, but, despite this similarity in one of their physiological actions, 

 they behave very differently toward the cells of the organism. Sac- 

 charin simply passes through the organism without entering into a 

 firm combination i. e., without being assimilated and is therefore 

 no food. Its sweetening action is due to a mere contact effect on the 

 cells sensitive to taste. Sugar, on the contrary, is actually bound by 

 the cells, assimilated and burnt, so that it is a true food. Ehrlich says 

 that the first requirement for every substance against which we can 

 obtain a specific serum must be its power to enter into such a combina- 

 tion with certain particular cells in the living organism. The substance 

 must possess a definite chemical affinity for certain parts of the organism. 

 Hence, in each substance against which we can specifically immunize, 

 Ehrlich assumes a group of atoms which effects the specific binding 

 to certain cells, the haptophore group (Fig. 67, F). Corresponding to this 

 is a group in the cell of the living organism C, the receptor group, with 

 which the haptophore group combines. The latter is entirely distinct 

 from that part of the substance which exerts the physiological or path- 

 ological effect, in toxins, for example, from the group which is the car- 

 rier of the poisonous action, the so-called toxophore group E, or in fer- 



