324 PATHOGENIC BACTERIA. 



substance in therapeutics was to produce immunity in 

 the patient without reactions, by gradual but rapid in- 

 crease of the dose. In so large a number of cases did 

 Koch produce immunity to tuberculosis by the adminis- 

 tration of TR, that he thinks it proved beyond a doubt 

 that the observations are correct. 



In making the TR preparation Koch advises the use 

 of a fresh, highly virulent culture not too old. It must 

 be perfectly dried in a vacuum exsiccator, and the tritu- 

 ration, in order to be thorough, should not be done upon 

 more than ioo mg. of the bacilli at a time. A satisfac- 

 tory separation of the TR from TO is said only to occur 

 when the perfectly clear TO takes up at least 50 per cent, 

 of the solid substance, as otherwise the quantity of TO in 

 the final preparation is so great as to produce undesirable 

 reactions. 



The fluid is best preserved by the addition of 20 per 

 cent, of glycerin, which does not injure and prevents 

 decomposition of the TR. 



The finished fluid contains 10 mg. of solid constituents 

 to the c.cm., and before administration should be diluted 

 with physiological salt solution (not solutions of carbolic 

 acid). When administering the remedy to man the in- 

 jections are made with a hypodermic syringe into the 

 tissues of the back. The beginning dose is ^^ of a mg., 

 rapidly increased to 20 mg., the injections being made 

 daily. 



In speaking of the results of experiments upon guinea- 

 pigs, Koch says: 



"I have, in general, got the impression in these ex- 

 periments that full immunization sets in two or three 

 weeks after the use of large doses. A cure in tubercu- 

 lous guinea-pigs, animals in which the disease runs, as 

 is well known, a very rapid course, may, therefore, take 

 place only when the treatment is introduced early — as 

 early as one or two weeks after the infection with tuber- 

 culosis. 



"This rule avails also for tuberculous human beings, 



