222 INFECTION AND RESISTANCE 



growing mass cultures of organisms, as advised by Hiss, in flasks 

 of glucose broth containing 1 per cent, calcium carbonate. 



The same method of growing micro-organisms is useful in the 

 case of streptococcus agglutinations, since the insoluble calcium car- 

 bonate, if thoroughly shaken, breaks the chains of streptococci and 

 thereby facilitates judgment as to the reaction. 



Agglutination reactions have been of considerable usefulness also 

 in the diagnosis of glanders in horses. The early work on this sub- 

 ject was done chiefly by MacFadyean, 9 and the reaction has been 

 particularly studied by Wladimiroff. 10 Since the serum of normal 

 horses will often agglutinate glanders bacilli in dilutions of as much 

 as 1-500, Wladimiroff advises making the positive diagnosis on dilu- 

 tions only higher than 1-1,000, since he states that normal horses may 

 occasionally reach an agglutination titre of 1-1,000. The same writer 

 states, moreover, that glanders bacilli are subject to great variations 

 in agglutinability, and that for this reason the choice of a suitable 

 strain is of great importance. 



The motility of bacteria has absolutely no relation to the reac- 

 tion, and their agglutination is entirely passive. 



Some of the earlier investigators of agglutination associated the 

 reaction with alteration in the flagellar mechanism of the micro- 

 organisms. It is now well known, however, that non-motile, as well 

 as motile, bacteria are subject to the phenomenon, and that no visible 

 change in the appearance or arrangement of flagella accompanies the 

 clumping. Although this is the case, observation of the motility of 

 such organisms as the bacillus of typhoid fever, while subjected to 

 the action of agglutinating serum, may be of great value in aiding 

 in the determination of the degree of completeness with which the 

 reaction is taking place. 



Agglutination, furthermore, does not lead to the death of the 

 bacteria. Of course, whenever the reaction is carried out in un- 

 heated serum the concomitant effects of the bactericidal substances 

 bring about bacterial death. Agglutination does not, however, 

 depend upon the cooperation of alexin, and serum may be inactivated 

 - without interference with its power of agglutination. In such heated 

 serum clumping takes place without bactericidal effects, and, more 

 than this, the bacteria may grow, if exposed to proper temperature 

 conditions, when suspended in the serum. In fact, it is of consider- 

 able interest to carry out the reaction in this way, for the bacteria 

 growing in agglutinating serum form long convoluted threads and 

 skeins even when in ordinary culture they habitually occur as sep- 

 arate individuals. Thus colon bacilli, typhoid bacilli, pneumococci, 

 cholera spirilla, and other organisms, which ordinarily grow as free 

 single cells, or, at most, in chains of two or three, if kept in the 



9 Macfadyean. Journ. of Comparative Path, and Ther., Vol. 9, 1896. 

 10 Wladimiroff. "Kolle u. Wassermann Handbuch," 2d Ed., Vol. 5. 



