IMMUNITY IN TUBERCULOSIS—FLEXNER. 645 
jection of tuberculin, when cautiously done, tends to bring about a 
rise in the tuberculous, of the “ opsonic index,” which Wright be- 
lieves is a measure of the good done, as an increase in immunizing 
substances in the blood is the cause of the rise. He also discoy bred 
that time is required for the occurrence of the rise and that the im- 
mediate result of the injection is a fall of the index—so-called neg- 
ative phase. This latter must be permitted to pass away and be 
succeeded by the positive phase before another injection is given. 
Gradually the “ opsonic index” is driven up in the cases that are 
favorable to the treatment. 
I do not intend to discuss the value to the clinician of this interest- 
ing method and Wright’s observations based upon it. The subject ap- 
pears to me to be one of great intricacy and therefore to be approached 
in a spirit of proper criticism despite its evident allurements. My 
purpose in mentioning it at all is to bring again to your attention a 
method of exciting the tuberculous body to put forth an effort at self- 
immunization which is sometimes efficient to a marked degree. It is 
n0t the injected tuberculin that accomplishes directly the changes in 
the condition of the patient, for there already exists, doubtless, an 
excess of similar poisons in the tuberculous foci in the body. The 
healthy body, indeed, does not react in this manner and is not to be 
protected, enduringly, from tuberculous infection by a previous treat- 
ment with tuberculin. As Koch’s phenomenon shows the tuberculous 
organism to have developed defenses against subsequent tuberculous 
infection which the normal body does not possess in equal degree, the 
employment of tuberculin indicates that the diseased body can be 
aroused artificially to put forth a stronger effort than its unaided 
natural forces enable it to make, in order that the disease may be 
overcome. Herein resides a great principle, an immense power for 
good, and, consequently, a great hope for future progress in the 
rational and specific treatment of tuberculosis in man. Efficient 
efforts at suppression of the causes of tuberculosis, deeper knowledge 
of the principles of bacterial immunity, are the two forces which in 
time may stay the ravages of the “ White Death.” 
