374 TYPHOID FEVER 



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

 isolated from typhoid cases, and we as yet do not know what 

 effect this circumstance may have on its subsequent sensitive- 

 ness to agglutination by typhoid serum. Again, Christophers 

 has pointed out that a large proportion of serum 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. 



With regard to the value of the serum reaction there is little 

 doubt. In nearly 95 per cent, of cases of typhoid it can be 

 obtained in such a form that no difficulty is experienced if the 

 precautions detailed above are observed. The causes of possible 

 error may be summarised as follows : The serum of the person 

 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, 

 as it is probable that all the forms which these take in men 

 have not been recognised. The very wide application of the 

 reaction has elicited the fact that it is given in many cases of 

 slight, transient, and ill-defined febriculte, 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. In conclusion, here we may say 

 that the fact of a typhoid serum clumping allied bacilli in no 

 way, so far as our present knowledge goes, justifies doubt being 

 cast on the specific relation of the typhoid bacillus to typhoid 

 fever. 



In connection with the phenomenon that a serum either from 

 a normal person or a typhoid patient may clump several varieties 

 of bacteria, some points arise. The theoretical consideration of 

 agglutination is reserved for the chapter on Immunity, but here 

 it -may be said that agglutinating properties may be present 

 normally in a serum or they may be originated by an animal 

 baing infected with a particular bacterium, As the result of 



