8o LABORATORY BACTERIOLOGY 



EXERCISE XXXVII 



WIDAL SERUM TEST 



125. This test depends upon the fact that when the blood 

 serum of a person suffering with typhoid fever, or who has 

 recently recovered from it, is added to a bouillon culture of the 

 bacillus, the bapilli become less motile and soon agglutinate in 

 small clumps. The dilutions used vary from equal parts of 

 serum anfl culture to dilutions of i to 50,000. It is recom- 

 mended that the stronger dilutions shall be used, i.e. those 

 from I : 10 to 1:50. The test has proven to be of much diag- 

 nostic value in typhoid fever. 



It has been found that a similar reaction will take place with 

 certain other bacteria when they are brought in contact with 

 the serum from animals suffering from the disease which they 

 produce. Thus it has been shown that such a reaction occurs 

 with hog-cholera bacilli and serum from affected or immunized 

 animals. 



On account of the diagnostic value of this reaction it is 

 employed very extensively in many health departments for the 

 diagnosis of typhoid fever. 



References. — Black, Johns Hop. Hosp. Bulletin, Dec, 1896. 

 Welch, The Jour, of the Am. Med. Asso., Aug. 14, 1897. Johnston, 

 N. Y. Med. Jour., Oct. 31, 1896. Med. News, Jan. 23, 1896. Biggs 

 and Park, The Am. Jour, of the Med. Sci., March, 1897. Wes- 

 brook and Wilson, The Phila. Med. Jour., March 36, 1898. Daw- 

 son, N. Y. Med. Jour., Feb. 20, 1897 (concerning hog cholera). 



126. Work for this Exercise Take i loopful of a fresh 



bouillon culture of typhoid bacilli (which will be furnished) 

 and place it on a cover-glass, add i loopful of blood serum 

 from a typhoid patient or the blood of an immune guinea pig, 

 and immediately make and examine a hanging-drop prepara- 

 tion with a loopful of the mixture. Note the effect on the 



