208 CLINICAL BACTERIOLOGY AND ILEMATOLOGY 



average index be taken as normal, it is unusual to find one 

 below o'95 or above 1*05. 



An important modification of the test is based on the fact 

 that a very considerable fluctuation of the opsonic index 

 takes place if the lesion is massaged, or, in many cases, if the 

 patient takes any exercise which has this effect. Thus in the 

 case of tubercle of the lungs the opsonic index should be 

 taken whilst the patient is at rest in the morning, then imme- 

 diately after suitable exercise (a walk of a mile or so, for 

 example), and again three or four hours after. In the case 

 of a joint it should be taken after rest, and then at intervals 

 after it has been massaged for some twenty minutes, with 

 a Bier's bandage applied above the joint. The importance 

 of this method of diagnosis is that there seems to be very 

 g'ood reason to believe that it< will show us whether the 

 disease is actually cured and not merely lying latent. Thus 

 in the case of tubercle of the lungs, if the index to tubercle 

 remains constant after reasonably severe exercise, the 

 patient is probably cured. The method has also important 

 applications in the diagnosis of tuberculous joints, glands, 

 etc., supposed gonorrhoea! lesions, and similar infections in 

 which no infective material can be obtained for examination. 

 The method is not an easy one, and must be carried out with 

 the most scrupulous care in these cases, and is best left to an 

 expert. 



A study of the opsonic index is the basis of Wright's 

 method of treatment by means of vaccines. In carrying 

 this out the patient's opsonic index is raised by injections of 

 the organisms which cause the disease (carefully sterilized) 

 in appropriate doses. These are given in a healthy part of 

 the body, where the tissues are stimulated to produce 

 opsonins against the organisms introduced, and these 

 opsonins are carried in the blood to the lesion. The reason 

 why it is thought necessary to estimate the opsonic index 

 of the blood from time to time in carrying out this process 

 is that the injection causes it to fall for a variable time 

 (usually a few days the negative phase), and if a second 

 injection be given before this fall has gone off and been 

 succeeded by a rise above the initial level, harm rather than 

 good will follow. 



The method of preparing these vaccines is roughly as 



