342 THE ALCALIGENES DYSENTERY TYPHOID 



(B) Macroscopic Method. Various dilutions of serum are placed 

 in small sterile test-tubes, 1 c.c. in each test-tube. As a routine, a 

 dilution of 1 to 20 is used, but a series of dilutions up to the limits 

 of the serum are frequently made. To each tube is added 1 c.c. of a 

 broth culture of typhoid bacilli. A control is made by adding 1 c.c. 

 of a broth culture of typhoid bacilli to 1 c.c. of salt solution. These 

 mixtures are respectively shaken and incubated together with the 

 control at 37 C. for two hours, then they are placed in the ice-box, 

 and examined eighteen to twenty-four hours later. A positive agglu- 

 tination is indicated when the supernatant fluid of the serum typhoid 

 mixtures is clear, while the control containing no serum remains 

 uniformly cloudy. 



The microscopic method is much more rapid than the macroscopic 

 method and is sufficiently accurate for ordinary purposes. The macro- 

 scopic method requires a much longer time, but it is more accurate, 

 for the dilutions can be made carefully with graduated pipettes. 



Discussion. Available statistics show that about 20 per cent, of 

 typhoid patients exhibit a positive agglutination reaction at the end 

 of the first week; 60 per cent, at the end of the second week; 80 per 

 cent, at the end of the third week; and 90 per cent, at the end of the 

 fourth week. These agglutinins persist; about 75 per cent, of all 

 patients exhibit a positive agglutination after two months. Occa- 

 sionally agglutinins may persist for several years. 1 The amount of 

 agglutination present, as indicated by the degree of dilution which 

 will still clump typhoid bacilli, has no known relationship to the 

 severity of the attack. An occasional mild case of typhoid may be 

 accompanied by the appearance of agglutinins of great potency; 

 severe attacks may exhibit little or no agglutinin in the blood. Occa- 

 sionally, agglutinins are not demonstrable in the blood serum of 

 undoubted cases of typhoid fever. This has been found to be the case 

 by Moreschi 2 in several cases of chronic leukemia. Moreschi 3 has made 

 the interesting observation that even the vaccination of these leukemics 

 with killed cultures of typhoid bacilli may not lead to the development 

 of agglutinins. In icterus an agglutination is not infrequently encoun- 

 tered even if the serum is highly diluted. It is very probable that at 

 least some of these cases are typhoid carriers, having typhoid bacilli in 

 the gall-bladder. They may be ambulatory cases. It has been claimed 



1 An initial negative reaction (first week) followed by a positive reaction is conclusive. 

 It rules out the possibility of persistent agglutinins from previous cases, and those due 

 to protective vaccination. 



2 Ztschr. f. Immunitatsforsch., 1914, xxi, 410. 3 Loc. cit. 



