392 A MANUAL OF BACTERIOLOGY 



hsemolytic system, p. 220) and incubated in the water-bath. The 

 process is repeated after five, ten, fifteen, and twenty minutes, 

 and longer if necessary. By the occurrence or absence of haemo- 

 lysis in the various tubes, the time taken for the absorption of 

 complement is ascertained, the complement used being that con- 

 tained in the serum itself, which therefore must be fresh. A 

 control with normal serum should always be performed at the 

 same time. With normal serum complete absorption should take 

 place in about twenty minutes ; with tuberculous sera it is often 

 complete in two and a half minutes. If, then, absorption of com- 

 plement is complete in much less than the time necessary for 

 absorption with a normal serum, presumably the serum is derived 

 from a tuberculous individual. (But see Emery's paper for 

 limitations. ) 



II. Precipitin reaction. Spengler has devised a precipitin 

 reaction for the diagnosis of, and prognosis in, tuberculosis. The 

 reagents are the blood-serum or the laked whole blood, or both, 

 very highly diluted and mixed in different dilutions with 

 tuberculin. 1 



III. Agglutination reaction. The method of agglutination was 

 proposed by Arloing and Courmont for the diagnosis of tuber- 

 culosis, but is difficult to carry out and is not much employed. 

 A special method has to be employed to obtain homogeneous 

 cultures of the tubercle bacillus or a powder of pulverised or 

 ground-up bacilli may be used : this powder may be purchased. 

 The reaction may be carried out macroscopically in small tubes. 

 For each test three dilutions of the serum are made, a 1 in 5, a 

 1 in 10, and a 1 in 20, and the tubes filled with these dilutions are 

 allowed to stand in an inclined position (45) for five to ten hours. 

 In man the serum of normal individuals may agglutinate up to a 

 dilution of 1 in 5, but not beyond. If agglutination occurs in the 

 1 in 10 or 1 in 20 dilution, the reaction is regarded as being 

 positive. 



A positive serum reaction in a suspected subject is a sign of 

 great value in establishing the diagnosis ; a negative serum 

 reaction is of less value. 



IV. The examination of sputum, etc., for the tubercle bacillus is 

 a routine procedure of the greatest value in forming a diagnosis. 



1 See Fearis, Practitioner, i.. 1913. 



