PRACTICAL APPLICATIONS 385 



week, and is gradually increased until 500 milligrammes ( = J c.c.) 

 of old or 2 milligrammes of TR is given. If a reaction occurs 

 an interval of a week is given, and the treatment recommenced 

 with a smaller dose. The dose of BE may be the same as that 

 of TR. 



There are numerous slight modifications in detail, but the fore- 

 going outline will serve as a general description of the process as 

 it is used in many of the Continental clinics. As a rule no 

 attempt is made to estimate the degree of immunity, but Koch 

 suggests the agglutination reaction for this purpose. It usually 

 rises to i : 100, or thereabouts, and may go much higher. 



As a result of the treatment, the patient is certainly immunized 

 to tuberculin, since he fails to react to fairly large doses. The 

 process is then stopped for a time and recommenced. The 

 beneficial effects as recorded (as I have seen on a small scale) are 

 undoubted, and the risks in careful hands and in properly selected 

 cases appear to be slight. 



2. The opsonic method consists in the use of such doses at such 

 intervals as will cause the maximum increase in the opsonic 

 index. The doses here are very much smaller than in the last 

 method. TR is usually employed, and the amounts range 

 between yo^Vc^ anc ^ IWQV milligramme. The idea, of course, is 

 to avoid the possibility of a summation of negative phases, and 

 to call forth the greatest possible formation of protective sub- 

 stances. It is extremely difficult to carry out, since the index 

 alters so quickly in most cases of progressive tubercle that very 

 frequent determinations of the index are necessary. Perhaps it 

 is the ideal method, and all who undertake tuberculin treatment 

 on a large scale ought to acquire some experience of it, but con- 

 siderations of time will prevent its ever coming into general use 

 as a routine treatment. In practice a sort of modified opsonic 

 method is sometimes used. The first few doses are controlled by 

 the index, and the optimum dose and interval determined. These 

 are then preserved throughout the treatment, with perhaps 

 occasional determinations of the index at times. 



It must be pointed out that the theoretical necessity for the 

 opsonic control depends on the acceptance of the fact that 

 tuberculin exerts its beneficial influence by causing an increase 

 in the amount of opsonins present in the blood. But this is not 

 certain. Admitting that the immunity is due to antibodies, these 

 may be bactericidal substances or anti-endotoxins, and we have 



