484 PATHOGENIC BACTERIA. 



ating power upon bouillon cultures of its respective 

 organism. 



Loffler and Abel also prepared a colon serum which 

 exerted a like specific action upon the colon bacillus, 

 but was without effect upon the typhoid bacillus. 



In 1896, Widal and Griinbaum, 1 working indepen- 

 dently, discovered that when blood-serum from typhoid- 

 fever patients is added to cultures of the typhoid bacillus 

 a definite reactive phenomenon occurs. This phenome- 

 non, which is now familiarly known as the "Widal re- 

 action," consists in complete loss of the motion so char- 

 acteristic of the typhoid bacillus, and the collection of 

 the micro-organisms into clusters or groups — agglutina- 

 tion. There seems, also, to be a change in the bacillary 

 substance, so that the bacteria appear shrunken and 

 distorted. 



Gruber and Durham 2 made the first thorough and sys- 

 tematic studies of the agglutinating and immobilizing 

 property of serum, beginning their publications in Janu- 

 ary, 1896. 



The work of Gruber and his associates is of great 

 importance, and merits careful reading and study. So 

 long as the matter was in Gruber' s hands, it was an 

 interesting scientific observation. In Widal's hands it 

 developed into a reliable means of diagnosing typhoid 

 fever and other diseases. 



For convenience, the subject will be considered under 

 separate divisions. 



The Time at ivhich the Reaction Develops. — The reac- 

 tion usually comes on about the seventh day, some- 

 times earlier ; and Johnston and McTaggart usually 

 found it quite well marked by the fifth day. They also 

 observed it in three cases at the end of forty-eight hours 

 from the beginning of the fever. Widal and Sicard state 

 that the reaction usually occurs on the first day of infec- 

 tion. Not infrequently the reaction fails to develop 



1 La Semaine medicate, 1 896, p. 295. 



2 Munch, tned. Woche7isci-ift, 1896, No. 13. 



