TWENTY-FIVE YEARS OF BACTERIOLOGY 135 



the antigen-containing fluid of the blood is enabled to 

 penetrate the extravascular tissues ; and on the basis of 

 this observed fact he has suggested that functional dis- 

 turbances of many organs of the body in sensitive human 

 subjects may be brought about in a similar manner. 



In a related field the hypersensitive reaction has been 

 employed to aid in the diagnosis of important diseases of 

 man and animals. It is apparent from what has been 

 stated of the site of the fatal anaphylactic shock in the 

 guinea pig, and as stated a moment ago of the sensitive- 

 ness of tissue cells in general to the circulating anaphylac- 

 tic antigen, that a visible local reaction might be obtainable 

 by introducing the protein to which the animal or person 

 is sensitive into a visible portion of the body, as say the 

 skin. In this way sensitiveness is looked for before serum 

 injections are given, tuberculin is employed to disclose 

 hidden foci of active tuberculosis, luetin is used to expose 

 evidences of latent syphilis, and, in a modified manner, 

 the Schick test is applied to determine whether exposed 

 children do or do not carry in their blood, spontaneously 

 as one might say, sufficient diphtheria antitoxin to afford 

 them security without a protective serum injection. And 

 beside the benefits accruing to human therapy directly 

 from the working out of the meaning of anaphylaxis are 

 to be placed those improvements introduced into veteri- 

 nary practice, from which human preventive medicine 

 also has derived great gain, namely, the application of the 

 tuberculin test in clearing milch herds of actively tuber- 

 cular cattle, and of mallein to the controlling of glanders 

 among horses. 



FlLTERABLES 



As we move from the contemplation of one achieve- 

 ment to another in bacteriology, we rarely pause to reflect 

 how far circumstances almost accidental have favored 

 the gains. The working out of the biological basis of fer- 



