WIDAL SERUM TEST 85 



EXERCISE XXXIII 



WIDAL SERUM TEST 



126. 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 bacilli become less motile and soon aggluti- 

 nate in small clumps. The dilutions used vary from equal parts 

 of serum and 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 i : 50. The test has proven to be of much 

 diagnostic 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, December, 



1896. Welch, The Jour, of the Am. Med. Asso., August 14, 



1897. Johnston, N.Y. Med. Jour., October 31, 1896; Med. News, 

 January 23, 1896. Biggs and Park, The Am. Jour, of the Med. 

 Sci., March, 1897. Wesbrook and Wilson, The Phila. Med. Jour., 

 March 26, 1898. Dawson, N.Y. Med. Jour., February 20, 1897 

 (concerning hog cholera). Cabot, Serum Diagnosis of Disease, 

 1899. Ruediger, The Jour, of Infect. Diseases, Vol. I, p. 236. 

 See also recent text-books. 



127. Work for this exercise. Take one loopful of a fresh 

 bouillon culture of typhoid bacilli (which will be furnished) and 

 place it on a cover glass, add one loopful of diluted blood 



