TYPHOID FEVER 75 



probability the appearance of the Widal reaction will soon settle 

 the matter. The other possible diagnoses are extremely unlikely. 

 The further identification of the bacillus is a matter of some 

 difficulty for which expert help should be obtained, or one of the 

 larger manuals of bacteriology consulted. 



The mesenteric glands and liver are, of course, not available for 

 the purpose of diagnosis. 



The demonstration of the baciUi in the urine is sometimes quite 

 easy, and might be of some diagnostic value. But they do not 

 always occur in this excretion, and the B. coli often does so, and 

 it is not easy to distinguish between the two. 



The only way in which typhoid fever can be diagnosed with 

 ease and certainty by a demonstration of the specific bacillus is 

 by an examination of material drawn directly from the spleen by 

 means of a hypodermic needle. The orgaxiism occnrs constantly in 

 this situation, and its demonstration is not difficult. The necessary 

 operation, however, is by no means devoid of risk, and is now 

 generally abandoned. 



This brings us to the method in which typhoid fever is now 

 usually diagnosed by the bacteriologist — Widal's reaction. This 

 reaction is a special example of a general law which was discovered 

 by Durham and others, and which is to the effect that the blood- 

 serum of a person who has been through an attack of a bacterial 

 disease will cause the specific organism of that disease to collect 

 into clumps. For instance, if we take a broth culture of the vibrio 

 of Asiatic cholera (which is turbid and opalescent) and add to it a 

 small quantity of blood-serum from a patient who has recovered 

 from an attack of cholera, we shall find that the culture becomes 

 clear, a sediment collecting at the bottom of the tube ; and if we 

 examine this sediment we shall find that it consists of felted 

 masses of the vibrios. This reaction is a general one, and is 

 given in most, if not all, bacterial diseases. But Widal, Griin- 

 baum, and others, working independently about the same time, 

 showed that, whereas in many diseases it is a reaction of immunity 

 {i.e., does not occur until late in or after the disease), in typhoid 

 fever it is a reaction of infection, and occurs so early in the course 

 of the disease that it is of great value in diagnosis. 



The test is applied by adding a small quantity of the serum 

 from the patient suspected to be suffering from the disease to a 

 larger amount of a young culture of typhoid bacilli, and watching 

 whether the appearance of the culture undergoes any change : it 



