238 THE PRINCIPLES OF IMMUNOLOGY 



presence of synergistic substances in the body; or to increased func- 

 tional susceptibility." 



The Tuberculin Test. In the course of his studies on the treatment 

 of tuberculosis, Koch devised the method of diagnosis which we now 

 speak of as the general tuberculin reaction, in contrast to the local 

 reactions subsequently discovered. It is now known that the introduc- 

 tion of tuberculin into the body may lead to local reactions both at the 

 site of inoculation and in the neighborhood of a tuberculous focus as 

 well as a general reaction which manifests itself in fever, headache 

 and malaise. Numerous methods of preparation of tuberculin for 

 therapeutic and diagnostic purposes have been described, but at the 

 present time the diagnostic methods, in' the hands of the majority of 

 workers, depend upon the use of original or old tuberculin of Koch. 



For the preparation of this tuberculin now designated as tuberculin O. T. 

 the organisms are grown for six to eight weeks on the surface of 5 per cent, 

 alkaline glycerine broth at 37 C. At the end of this time the entire contents 

 of the flask are sterilized and concentrated to about one-tenth of the original 

 volume by means of a current of live steam and a water bath. The glycerine 

 does not evaporate, and as a result of the concentration constitutes 50 per cent, 

 of the final mass. This is filtered through porcelain and the filtrate employed. 

 Koch subsequently made other preparations, particularly the tuberculin 

 known as T. R. and that known as B. E. The T. R. or tuberculin residue is 

 prepared by growing virulent tubercle bacilli on nutrient glycerine broth for 

 four to six weeks at 37 C. The bacilli are obtained by filtration, dried, and 

 ground in a mortar. One gram is washed with 100 c.c. distilled water, the 

 precipitate is again dried, powdered and repeatedly washed in small volumes 

 of water until no sediment results. The watery extract constituted by this 

 second series of washings, which should not exceed 100 c.c., is preserved with 

 20 per cent, of glycerine and constitutes the T. R. The bacillus emulsion 

 (B. E.) is prepared by growing the organisms as indicated in the preparation 

 of the original or old tuberculin. The bacilli are obtained by filtration, ground 

 in a mortar and emulsified in 100 parts of distilled water to which is added an 

 equal amount of glycerine. 



Numerous other methods of preparing extracts of the tubercle 

 bacillus have been described but are, in essential, modifications of 

 the methods of Koch. At the present time the original or old tuber- 

 culin is used most widely. 



The General Reaction. As a general rule, the old tuberculin is put on 

 the market in the form of ampoules of fluid, i.o c.c. of which represents i.o 

 gram of pure tuberculin. This may be diluted for the actual test. Inasmuch 

 as individual sensitiveness varies considerably, the primary dose should be 

 very small. According to Hamman and Wolman, three classes of patients 

 may be recognized, (a) children, (b) patients who have a slight fever or are 

 not in good general condition, (c) patients in good condition. The smaller 

 doses are given to children and the largest dose to patients in good general 

 condition. Upon this basis the initial dose of old tuberculin should be 

 0.000,000,1 c.c. to 0.000,001 c.c.; failing to obtain reactions with these doses, 

 subsequent tests may be made at intervals of about a week, increasing the 

 dose each time. Although it is possible to give a maximal dose of i.o c.c. of 

 the dilution, it is rarely advisable to exceed 0.05 c.c. The injections should 

 be given under strict aseptic precautions, and appear to be most satisfactory if 

 given at the lower angle of the scapula. They are probably best given in the 

 afternoon, after the patient's afternoon temperature has been taken, so as 

 to avoid the confusion of an unusually high elevation of temperature on the 

 day selected. The reaction appears as a rule in from twenty-four to thirty- 

 six hours. It may appear as late as forty-eight to sixty hours. A positive 

 reaction is indicated by an elevation of temperature of about 2 to 4 C. In 



