400 CHOLERA 



peptone solution, and two hanging-drop preparations are made, 

 one with the addition of normal serum in i : 50 dilution, the 

 other with a i : 500 dilution of a powerful anticholera serum, 

 such as can be obtained commercially. Cholera vibrios become 

 paralyzed and agglutinated in the second specimen, not in the 

 first. When smaller numbers are present a culture (probably 

 impure, but with the vibrios in sufficient abundance to serve for 

 the test) may be made by incubating peptone-water inoculated 

 with a flake of mucus for eight to twelve hours. This is to be 

 tested with the serum in the ordinary way, and should agglutinate 

 at nearly the same dilution as a known cholera culture. The 

 serum should be a powerful one, clumping at i : 10,000 or 

 more. 



The Pfeiffer's reaction is perhaps more conclusive, and is 

 carried out as follows : The test immune-serum is diluted with 

 broth or normal saline, so that i c.c. contains o-ooi c.c. of serum; 

 i c.c. of this fluid is used to emulsify a loopful of a young agar 

 culture of the suspected organism, and the emulsion injected 

 intraperitoneally into a young guinea-pig. After a few minutes a 

 little peritoneal fluid is withdrawn by means of a capillary tube, 

 and the vibrios will be seen to have become non-motile, and to be 

 undergoing the characteristic change into slightly refractile 

 rounded masses. After a short time more they will be found 

 to have disappeared altogether. A control experiment with 

 normal serum may be made. This test is of great value, many 

 closely allied organisms failing to react. But no test is absolutely 

 conclusive, since a few cultures (notably the El Tor vibrio) have 

 been found to give all or most of them, and yet have been isolated 

 in a region in which cholera is not known to occur. The subject 

 is not yet settled, but in the meantime the probability that any 

 organism which reacts positively to the agglutination and 

 Pfeiffer's tests is true cholera is enormous. 



The serum of persons convalescent from cholera agglutinates 

 the vibrios at dilutions of i : 100 or more for some months after 

 the attack, a fact which may be of some value in determining 

 the nature of a previous disease and a possible immunity to 

 cholera. 



As regards treatment, the ordinary bacteriolytic serum is quite 

 useless, and, as far as I am aware, no potent anti-endotoxic serum 

 has been tried. The prophylactic treatment is on a sounder 

 footing. It was introduced by Ferran, of Barcelona, as early as 



