96 PRINCIPLES OF BACTERIOLOGY 



in the vicinity than in the case of the extracellular toxins. These sub- 

 stances are extracted by the method proposed by Koch and Buchner, 

 of first crushing the bacteria in a moist or dried condition, and then of 

 obtaining their contents with the aid partly of the hydraulic press. 

 In this way a large series of impure bacterial proteids was obtained, 

 which, though differing in some respects, exhibited mainly the same 

 properties. 



Altogether different from these poison effects are the immunization 

 processes produced by the cell substances of bacteria, whether they be 

 obtained from bacterial bodies or from chemical preparations. These 

 processes have nothing to do with the toxic action of the cell proteids, 

 but rather depend upon the introduction of suitable receptors which 

 give rise to the bactericidal protective powers lysin, precipitin, and 

 agglutinin. 



For the present we may assume with certainty that such receptors 

 exist only in the unchanged bacterial cells, which, like cholera vibrio, 

 pneumococcus, etc., give up in toto their destructive processes; on the 

 other hand, we may say pretty surely that forcible extraction that is, 

 production of chemical proteid preparation so changes most of the 

 atomical grouping that little or no bactericidal reaction results from 

 their introduction, and that these albuminous substances produce only 

 the same reaction as other outside albuminous substances i. e., the 

 formation of a specific precipitin, which, however, is closely allied to 

 agglutinin. It is very probable, on the contrary, that in the substance 

 so carefully prepared as Koch's tuberculin and Buchner's plasmin, from 

 the tubercle bacillus and the cholera vibrio, the specific receptors may 

 be retained, so that these preparations produce bactericidal arid immuni- 

 zation processes. 



SUMMARY. 1. One group of bacteria produces as free secretions 

 true toxins. After extraction of this soluble poison there remains a pure 

 unspecific bacterial residue. Type: diphtheria. 



2. Another large group possesses apparently only endotoxins, true 

 toxins which are more or less closely bound to the living cell, and which 

 are only in a small degree separable in unchanged condition perhaps 

 outside of the body. On death of the cell they become partly free, 

 partly remain united, or become secondary poisonous modifications 

 no longer of the nature of toxins. In this group, therefore, the dead 

 cell bodies cannot be entirely freed without residue from the poisons; 

 the pure proteid cannot be clearly identified by its individual action, i 

 With this reservation, however, the proteid action can be demonstrated. 

 Type: cholera, typhoid, pneumococcus. 



3. A third group yields perhaps no true toxins, not even intraplas- 

 matically. The cell plasma contains poisons of another kind which 

 obscures the typical proteid action. Type: anthrax, tuberculosis. 

 Possibly by further investigation Groups 2 and 3 may be united. 



The pyogenic action of their proteids is common to all bacteria, i 

 this depending principally upon their being extraneous albuminous 

 substances. Pyogenic effects may be produced in like manner by 



