292 TUBERCULOSIS 



bacilli. Now, in order to get permanent benefit from the vac- 

 cination 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 vaccina- 

 tion 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. There are very great variations in the capa- 

 cities 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 continued 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 with- 

 out the purposive quality which ought to characterise a success- 

 ful 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 certain patients a fall in 

 the opsonic index after muscular exertion. For ordinary cases 

 with low opsonic index and no evidence of constitutional dis- 

 turbance, an amount of tuberculin corresponding to from one- 

 thousandth to a six-hundredth of a milligramme of tubercle 

 powder is a sufficient dose, and if any dose seems to produce a 

 pronounced negative phase, then a smaller dose ought to be tried 

 at the next inoculation. For cases clinically tubercular, where 

 the index is about normal, then smaller doses, say, the equivalent 

 of a two-thousandth of a milligramme or less, ought to be used, 

 the effect on the index being carefully watched. In any case, 

 the dose which is found to give the highest positive phase is the 

 optimum dose, and one which need not necessarily be increased. 

 Cases where there is constitutional disturbance should be as a 

 rule left untreated. 



With regard to the results obtained, many cases have been 

 brought forward by Wright and others where benefit has 

 followed the putting into practice of the principles enunciated, 



