TYPHOID FEVER 7I 



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 typhoit 

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

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



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

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

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

 whether the appearance of the culture undergoes any change : i 

 may be watched under the microscope or by the naked eye, th 

 technique differing in the two cases. The microscopic method i 

 rapid and requires a very small amount of blood, and is no'v 

 generally used. The macroscopic method is perhaps somewhat easie 

 for a beginner, but it takes a longer time and requires a large 

 amount of blood-serum. 



The technique in either case is readily learnt, and can b 

 carried out with very little difficulty if the materials are at hanc 

 But the test is one which it is seldom advisable for the horn 

 worker to attempt, as it requires a young culture of typhoi 

 bacilli. We shall, however, describe the process, as some ma 

 carry it out during an epidemic, or if they are Hving where the 

 have not access to a pubHc laboratory. The process has no' 

 been greatly facilitated by the demonstration of the fact (b 

 Widal) that the reaction is given with dead cultures of the bacill 

 These cultures can be obtained from any bacteriological laborator 

 and will keep. They are prepared by adding 4 or 5 c.c. 1 

 the following fluid to an eighteen-hours-old culture of typho: 

 bacilli, scraping off the growth, pipetting the emulsion into 



