INFECTION AND INTOXICATION. 89 



been observed in infection by the Bacillus coli commu- 

 nis, Bacillus icteroides, bacillus of hog cholera, of teta- 

 nus, of tuberculosis, etc. The reaction is, as a rule, 

 specific; that is, it results from the action of serum from 

 a certain infection upon the bacteria of that particular 

 infection. In many cases serum may appear to cause 

 agglutination with various related bacteria, but when the 

 blood is properly diluted it is almost invariably the case 

 that the bacteria of the particular infection under con- 

 sideration are sensitive to the action of the serum in 

 dilutions far greater than those that have ceased to act 

 upon the related bacteria. In this way the phenomenon 

 of agglutination more or less perfectly fulfils the double 

 purpose of a differentiating test for similar bacteria and a 

 method for recognizing different diseases. 



The cause of the phenomenon is not explained. It 

 seems to have nothing to do with immunity. The ag- 

 glutinating substance is present in all the normal and 

 pathologic fluids of the infected animal, making its 

 appearance some time after the inception of the process, 

 though occasionally very promptly. It is present through- 

 out the course of the disease, and may remain for many 

 years afterward. 



The formation of agglutinations probably does not in- 

 dicate any important cellular or vital reaction, as they 

 may follow the addition of various chemic agents to cult- 

 ures of the bacteria, and may depend upon metabolic 

 products of the bacteria themselves, for they sometimes 

 occur spontaneously in highly vegetative cultures. Mal- 

 voz l found that the metabolic products contained in the 

 cultures would produce the agglutinations. His experi- 

 mental evidence consists in thoroughly mixing a fresh 

 culture of the first vaccine of anthrax in \ c.c. of dis- 

 tilled water, and adding to it a loopful of a six-day-old 

 culture. A drop of the mixture allowed to stand for a 

 few hours in a moist chamber will show typical agglu- 

 tinations when examined under the microscope. 



1 Ann. de V Inst. Pasteur, Aug. 25, 1899. 



