BACTERIOLYSIS AND ALLIED PHENOMENA 2OI 



finding one that can be reactivated by human complement, and 

 has suggested the use of serum from the higher apes, the com- 

 plements of which closely resemble those of man. These 

 explanations are not very satisfactory. Thus Shiga's antidysentery 

 serum is certainly readily complemented by human blood; and 

 although it has certainly some beneficial action, it is useless in 

 the chronic stages of the disease, and this although the amount 

 injected must be very much greater than is necessary to dissolve 

 all the bacilli present in the body. 



Another possible cause of failure is the deviation of complement. 

 If we admit the action of the bactericidal substances by no 

 means undisputed in the natural process of recovery from 

 disease, we can easily see how it is that this process does not 

 occur under normal conditions. Thus, when infection with the 

 typhoid bacillus occurs, there is at first little or no amboceptor 

 in the blood. The small amount present is quickly seized by 

 the bacteria and removed, and although a few bacilli may be 

 killed, the great majority flourish unchecked. But amboceptor 

 is soon put out in gradually increasing amounts, and at first is 

 used up as soon as it is formed. The two processes, proliferation 

 of bacilli and increase in the amount of amboceptor, now progress 

 side by side, and on their relative rapidity depends the outcome 

 of the disease. At first bacillary proliferation takes place more 

 rapidly than the production of antibody, and the symptoms 

 gradually become more and more severe. After a time the 

 antibodies are released in larger and larger amount, and (in a 

 favourable case) a time arrives when there is exactly enough 

 for all the bacteria present. We must assume that enough 

 complement is available, and in this case it is easy to see how 

 it can never become deviated ; for all the amboceptor is rapidly 

 linked up to the bacilli, and does not accumulate in excess in the 

 blood. It does seem possible, however, that an accumulation of 

 amboceptor might conceivably determine a relapse, bacteria 

 which escaped destruction owing to their having lain in the 

 tissues, gall-bladder, or other inaccessible region, being now free 

 to grow in the blood owing to the removal of complement by 

 deviation. 



But when a dose of bactericidal serum, containing, it may be, 

 many times more immune body than is necessary for the solution 

 of the bacilli present, is suddenly thrown into the circulation, 

 the conditions are quite different. Here there is an excess of 



