OPSONIC INDEX AND VACCINE THERAPY 355 



especially when the vaccine is to be extensively used, as in typhoid 

 immunization, inject some of the vaccine into white mice to exclude 

 the possibility of contamination with tetanus. In such cases also it 

 is not inadvisable to test out the antigenic value of the vaccine upon 

 animals, measuring the agglutinins, etc., which result from a number 

 of inoculations. In the preparation of a therapeutic vaccine where 

 speed is required this of course is not feasible. Moreover, it is un- 

 necessary in view of the fact that we wish to inject that particular 

 organism into the patient from whom it has been cultivated. What- 

 ever its antigenic value may be from animal experiments, it is pre- 

 ferable for the given purpose to any other strain. 



Sensitized vaccines are easily made by exposing emulsions of the 

 bacteria to moderate amounts of a strong immune serum which has 

 been heated to 56 C. to destroy the complement. Bacteria will 

 usually agglutinate under these circumstances and can easily be 

 centrifugalized to the bottom. The excess serum is then washed off 

 and the bacteria emulsified as in the case of the preparation of vac- 

 cines with dead organisms. 



THE TUBERCULINS 



Since we shall not attempt to discuss critically tuberculin treat- 

 ment, as this is a subject upon which many special studies have been 

 made both by clinicians and by laboratory workers, and is entirely 

 too extensive to be reviewed in a book like this, on the other hand, 

 we deem it a, part of our task to discuss at least the methods by which 

 the antigen or tuberculin preparations are obtained. There has been 

 much discussion concerning the nature of the antigenic substances 

 obtained from the tubercle bacillus. It has been claimed by Denys 

 and others, for instance, that the tubercle bacillus may give rise to 

 small quantities of a true exotoxin with consequent endotoxin- 

 inducing properties. Again, most observers have believed that the 

 poison of the tubercle bacillus consists of substances comparable to 

 the endotoxin of other micro-organisms. The matter is by no means 

 settled, and without going into the theoretical aspects of the problem 

 we will confine ourselves in this place to a description of the pro- 

 duction of the various forms of so-called "tuberculin." 



OLD TUBERCULIN (Keen) 



The first tuberculin prepared by Koch is made in the following 

 way : Tubercle bacilli of the human type are grown for from 4 to 6 

 weeks upon a 5 per cent, glycerin broth. The cultures are then 

 sterilized in an Arnold sterilizer and are evaporated at about 80 C. 



