262 TUBEECULOSIS 



vaccine is followed by a decrease in the opsonic qualities of the 

 serum, the occurrence of a negative phase. J)uring such a 

 period of depression there is probably an increased susceptibility 

 to the action of the bacilli. Now, in order to get permanent 

 benefit from the vaccination process, repeated injections of the 

 tuberculin must be practised, and if an injection be given during 

 a negative phase, actual harm may be done. The course of a 

 successful vaccination is that, after the passing off of the negative 

 phase, the opsonic index should rise to above its original level, 

 the occurrence of a positive phase. It is when this positive 

 phase is fully developed that a fresh inoculation can be practised 

 with success. The new negative phase which will now occur 

 may not cause a drop to below the level of the original state of 

 the serum, and the hope is that its succeeding positive phase 

 will carry the opsonic index still higher and ensure a still greater 

 resistance to the bacterium. The importance of the observations 

 of the opsonic index lies in this that in antibacterial vaccina- 

 tions the degree of active immunisation which can be attained is 

 always much less than is the case with immunisation against 

 such a substance as the diphtheria toxin, although in the latter 

 there also occur negative and positive phases of a precisely 

 similar character. If an injection be practised during a negative 

 phase, then a still further drop in the opsonic content of the 

 serum will occur and a fresh growth of the invading bacilli is 

 likely. There are very great variations in the capacities shown 

 by tubercular patients to react to a vaccination process. In certain 

 cases good positive phases are readily and quickly produced, while 

 in others after an inoculation the negative phase is long con- 

 tinued and may even show no tendency to pass into a positive 

 phase. The irregularities in the opsonic index in cases where 

 there is a general disturbance of metabolism Wright explains by 

 supposing that they result from very irregular auto-infections of 

 the patient's body by tubercular products from the local lesions, 

 positive and negative phases being produced without the pur- 

 posive quality which ought to characterise a successful therapeutic 

 vaccination. Such auto-infections may come about in various 

 ways, and Wright is of opinion that exercise, for instance, may 

 disseminate both tubercular products and tubercle bacilli, he 

 having noticed in tubercle patients a fall in the opsonic index 

 after muscular exertion. 



With regard to the details of the immunisation, Wright's 

 chief point is that the repeated, uncontrolled injections of tuber- 

 culin such as were originally given may very likely have a harmful 

 result, and that when an injection is practised it is not necessary 



