Precipitin Reaction. 723 



of varying but definite size, that have been saturated with serum, are placed in the 

 fluid. In this manner varying dilutions of serum are produced in the test fluid, 

 which is then incubated for 24 to 48 hours or allowed to stand near a warm stove. 

 The agglutination titers may then be determined by comparing the results in the 

 tubes with a properly tabulated guide. 



3. Precipitin Reaction. In this phenomenon the serum of 

 an immunized animal produces a fine flaky precipitate in the 

 culture filtrate of the organism used in immunization. It was 

 first observed by Kraus, subsequently by Wladimiroff, who 

 noted that it occurred also in filtrates of glanders cultures 

 after the addition of serum from glanderous horses. The 

 latter 's observation was confirmed l)y Pfeiler, Miessner and 

 Muller, although the investigations of the latter showed that 

 the sera of healthy horses also produced precipitates (normal 

 precipitins) but in a less degree, thus causing more or less 

 confusion in diagnosis. On the other hand they olitained better 

 results when they used bacillary extracts or mallein solutions 

 instead of culture filtrates and instead of mixing these with 

 the serum gently pouring them on the surface of the same (con- 

 tact or ring test). By this latter method a distinct gray l3and 

 of precipitate which may be regarded as quite specific, will 

 form within a few minutes at the line of contact of the two 

 fluids. According to observations thus far recorded this method 

 is giving satisfactory results in most instances while the fact 

 that precipitins can be demonstrated also in chronic cases of 

 disease presents an additional advantage. 



Pfeiler, who uses extract of glanders bacilli prepared with carbol-sodium- 

 chloride solution or carbolized horse serum as a precipitinogenic fluid, tested 452 

 blood samples obtained from 306 horses suspected of the disease or exposure thereto. 

 He compared his results with those obtained by the agglutination and complement 

 fixation tests and found that they confirmed each other, particularly in recent cases 

 of infection. In experimentally infected horses the precipitins could be demon- 

 strated within 4 or 5 days after infection. Similarly favorable results were obtained 

 by Miessner in IS glanderous horses by the use of extract of glanders bacilli and 

 10% mallein solution made with Foth's dry mallein. In very old cases only were 

 the results from this method less satisfactory. Finally, Muller was able to deter- 

 mine the specificity of the reaction in his guinea pig experiments. 



Other Diagnostic Methods. In former times the following were frequently 

 resorted to: The inoculation of a suspected horse with its own secretions, a healthy 

 portion of the body being selected to reproduce the characteristic, glanderous 

 lesions; trephination of the antrum of Highmore, in order to permit direct inspec- 

 tion of its mucous membrane; the artificial production of a fever or of the acute 

 form of the disease by subjecting the suspected animal to hard work' or by the 

 subcutaneous injection "of oil of turpentine (Caguy) or by the injection of strepto- 

 coccus cultures (Jewsejenko). In any of these methods only a positive result had 

 any value, and all of them have long been superseded by modern methods of 

 diagnosis. 



In more recent times Baldoni and Dieckerhoff recommended the intravenous 

 injection of Crede's colloidal silver, which produces a febrile reaction in glander- 

 ous horses and consequently might be of service in the diagnosis of doubtful cases. 

 Eoder, Passau and Blomehave also observed this action, although Poetschke and 

 subsequently also Eoder observed that a similar reaction occurred occasionally in 

 the course of other internal and external diseases and even in healthy horses. 



Carrozo recommends Ehrlieh's diozoreaction (red coloration of the urine 

 after the addition of hydrochloric sulphanilic acid, potassium iodide and ammonia), 

 this reaction being much more pronounced in the urine of glanderous horses than in 



