21 235 



its power of agglutinating bacteria. The figures given in Series 77, Tal)le XXIII, 

 make it quite plain that it is impossible to find any connection between the sugar- 

 inverting power of various acids and their power to agglutinate B. coli. It can here 

 be seen, for example, that while hydrochloric acid has 21 times the sugar-inverting 

 power of monochloracetic acid, it only possesses Vt of its power to agglutinate 

 H. coli. There is one point serving to differentiate agglutination by an acid from 

 that due to an immune-serum that may be mentioned here, which is that bacterial 

 suspensions that have been freed from excess of salts by dialysis can be agglutin- 

 ated directly by an acid, while an immune-serum can only pioduce agglutination 

 when a salt has been added to the mixture. Thus agglutination by an acid does 

 not demand that a salt should be present in quantities that can be readily detected 

 by chemical means. 



Before leaving the subject of agglutination by acids, it may be worth while 

 to record briefly the action exerted upon its course by the addition of the normal 

 serum of a horse; for this illustrates the conditions obtaining when an immune- 

 serum is used for agglutination after it has been treated with an acid, and may 

 help in the elucidation of the phenomena there observed. Table XXIV records the 

 results of a single experiment; an emulsion of a 24-hour agar-culture of B. coli 

 was divided into 4 parts, to 3 of which normal horse-serum was added in the pro- 

 portion of 10, 1 and Vio parts per mille; acting by itself, this horse-serum was 

 very feebly agglutinative, 02 com. being required to produce the minimum visible 

 agglutination in loc.cm. B. coli suspension, a (piantity corresponding to 80 percent 

 of the 2'5 c.cm. present (as previously explained) in each test-tube. This horse-serum 

 was not added to the emulsion used in column A, which therefore served as the 

 control series. The experiment was then made of producing acid-agglutination in 

 the 4 sets of tubes, using HCl as agglutinant in the same amounts as in the experi- 

 ments already described. It was found that quantities of HCl varying between 

 365 and 073 milligrams per tube produced a feebler degree of agglutination in the 

 control-series A than was present in the tube selected as standard (denoted S), 

 while in the columns B and C no agglutination at all was produced by from 3-65 

 to 04745 mgrm. HCl. In column D on the other hand, a weak degree of agglutin- 

 ation was produced by from 365 to 219 |niilligrams of HCl, while no trace of 

 agglutination at all was produced by from 1-825 to 04745 milligrams of the acid. 

 It is further seen that the smallest amounts of acid producing agglutination in the 

 4 sets of tubes were 004745 mgrm. in the two sets A and D, and 006205 mgrm. 

 in C, and 009125 mgrm. in B. 



In other words, this experiment shews that when present in quantities of from 

 10 to 001 per cent, normal horse-serum can lessen or prevent the agglutinating powers 

 of both large and small quantities of acid, that are able to produce agglutination in 

 the control-series of test-tubes, but that it may be without influence upon the inter- 

 mediate amounts of the acid. 



