178 PRINCIPLES OF BACTERIOLOGY 



when a simultaneous infection with paratyphoid was excluded. This 

 agglutination for the other bacilli was in some cases quite marked, 

 though there was no uniformity whatever. Since he found that, con- 

 versely, in paratyphoid infection the serum possesses a fairly strong 

 agglutinating action on typhoid bacilli, Korte advises that in every case 

 of typhoid all three bacteria be tested for agglutination, so that, accord- 

 ing to the strongest agglutinating action, one can decide which infection 

 is present. If in practice it is immaterial whether this point be decided, 

 the agglutination with paratyphoid need only be undertaken when the 

 typhoid agglutination is absent. 



In all this we are dealing with the same phenomenon which undoubt- 

 edly plays a role in the agglutination with blood of icteric patients, the 

 so-called group agglutination, as it was first termed by Meinhard Pf aund- 

 ler. 1 In other words, while agglutinins may be nearly, if not quite, 

 specific in their action a serum which produces agglutination may be 

 far from being so. As a rule, the agglutination with the infecting agent 

 is by far the strongest i. e., it proceeds even in high dilutions whereas 

 other bacteria require a stronger concentration. The bacteria which 

 are agglutinated by one and the same serum need not at all be related in 

 their morphological or other biological characteristics, as at first assumed. 

 Conversely, micro-organisms which, because of the characteristics men- 

 tioned, are regarded as entirely identical or almost so, are sharply 

 differentiated by means of their agglutination. In other words, the 

 "groups" arrived at by means of a common agglutination have no 

 relation to species as the term is usually employed. Thus, according 

 to Stern, certain varieties of proteus and of staphylococci excite the 

 production of sera which exert marked agglutinating powers also on 

 typhoid bacilli, although otherwise we do not regard these three micro- 

 organisms as at all related. Because of this lack of absolute specificity 

 the serum diagnosis of infection or identification of bacteria has value only 

 when very carefully tested. 



The Relative Development of Specific and Group Agglutinins. The 

 study of a large number of series of agglutination tests obtained from 

 young goats and rabbits injected chiefly with typhoid, dysentery, para- 

 dysentery, paracolon, colon, and hog-cholera cultures has shown that 

 there is considerable uniformity in the development of the specific and 

 group agglutinins. The specific agglutinins develop in larger amount 

 in the beginning, being in the second week usually from five to one 

 hundred times as abundant as the group agglutinins. Later the total 

 amount of the group agglutinins tends to approach more nearly to 

 that of the specific, and reach as high as 50 per cent. In a number of 

 tests carried out by us we found that many group agglutinins supple- 

 ment specific ones in their action, causing by their addition an increased 

 agglutinating strength. In our experience the variety of micro-organ- 

 ism used for inoculation is, if equally sensitive, agglutinated by the com- 

 bined specific and group agglutinins produced through its stimulus 



1 Ueber Gruppenagglutination und das Verhalten des Bacterium coli bei Typhus, Munch, med. 

 Wochenschrift, 1899, No. 15. 



