228 BACTERIOLOGY FOR NURSES 



the Straus reaction, and sero-diagnostic tests are the most fre- 

 quently employed. 



Mallein Reaction. Mallein is a concentrated glycerin broth 

 in which B. mallei has been cultivated and is prepared in exactly 

 the same manner as tuberculin. After a subcutaneous injection 

 a positive reaction in a glandered animal is manifested by a rise 

 in temperature of about two degrees, a tender local swelling at the 

 point of inoculation, and a general disturbance, while in healthy 

 horses the temperature does not rise above one degree and the 

 local swelling is slight and soon disappears. 



It has been recently shown that mallein dropped into the con- 

 junctival sac gives a similar reaction to the ophthalmic test in 

 tuberculosis. Three drops of mallein dropped into the eye of a 

 glandered animal will cause a swelling of the eyelid and a purulent 

 discharge from the tested eye in from five to six hours. The test 

 is so simple and gives such a reliable and quick result that it has 

 been adopted as the Federal test for the interstate shipment of 

 horses. 



The Straus reaction consists in injecting into the peritoneal 

 cavity of a male guinea pig some of the suspected material. If 

 virulent glanders bacilli are present, enlargement of the testicles 

 and pus formation occurs within two to five days. A positive 

 reaction together with the presence of typical organisms in the 

 lesion is proof positive of the disease. Failure on the part of the 

 guinea pig to react, however, does not preclude the possibility of 

 the disease. 



Serum Reactions. The serum of an infected horse possesses 

 a very high power of agglutination ; a dilution of 1 to 1000 or higher 

 will react positively. Since normal serum will agglutinate the 

 bacilli in dilutions as high as 1 to 500, three dilutions of serum 

 from a suspected animal are generally employed : 1 to 500, 1 to 

 800, and 1 to 1000. If agglutination occurs only with the first 

 dilution the reaction is considered negative; with the first and 

 second, doubtful ; with the first, second, and third, positive. 



Complement fixation tests give probably the most reliable 

 results of all. According to certain workers a positive reaction is 



