VACCINATION AGAINST TYPHOID 375 



may naturally have the capacity of clumping typhoid bacilli ; 

 there may have been an attack of typhoid fever previously with 

 persistence of agglutinative capacity ; the case may be one of 

 disease caused by an allied bacillus ; the disease may have a 

 quite different cause, and yet the serum may react with typhoid 

 bacilli; the disease may be typhoid fever and yet no reaction 

 may occur. The most important of these sources of error is that 

 with which diseases caused by allied organisms are concerned 

 (see p. 390). The very wide application of the reaction has 

 elicited the fact that it is given in many cases of slight, transient, 

 and ill-defined febripulae, which occur especially when typhoid 

 fever is prevalent. Some of these may be aborted typhoid, 

 some may be paratyphoid. There is no doubt that, if all the 

 facts are taken into account, the cases where the reaction gives 

 undoubtedly correct information so far outnumber those in 

 which an error may be made that it must be looked on as a 

 most valuable aid to diagnosis. 



Tlie Agglutination of Organisms other than the B. typhosus by Typhoid 

 Serum. — Though many races of the b. coli give no reaction with a 

 typhoid serum, there are others which react positively. Usually, how- 

 ever, a lower dilution and a longer time are required for a result to be 

 obtained, and the reaction is often incomplete. It has also been found 

 that other organisms belonging to the coli-typhoid group react in a 

 similar way. The important point here is the determination of the 

 highest dilution with which clumping is obtained (see p. 392, and for 

 methods, see p. 390). There is a point in this connection regarding 

 which further light is required. Many races of b. coli in use have been 

 isolated from typhoid cases, and we as yet do not know .wj^i effect this 

 circumstance may have on its subsequent sensitiveness to agglutination by 

 typhoid serum. - Again, Christophers has pointed out that a large pro- 

 portion of sera from normal persons or from those suffering from 

 diseases other than typhoid will clump the b. coli in dilutions of from 

 1 : 20 to 1 : 200, and no doubt many of the reactions shown by typhoid 

 sera towards b. coli are due to the pre-existence in the individuals of an 

 agglutinative property towards the latter bacillus. 



Vaccination against Typhoid. — The principles of the im- 

 munisation of animals against typhoid bacilli have been applied 

 by Wright and Semple to man for prophylactic purposes. The 

 method of preparing the vaccine has been described on p. 131. 

 Two doses are usually given separated by an interval of ten 

 days. The first consists of 500,000,000 bacilli and the second 

 of 1,000,000,000. The effects of the first injection are some 

 tenderness locally and in the adjacent lymphatic glands, and 

 it may be local swelling, all of which come on in a few hours, 

 and may be accompanied by a general feeling of restlessness 

 and a rise of temperature, but the illness is over in twenty-four 



